This has been CNBC's live blog covering updates on the war in Ukraine. Follow the latest updates here.

Russian missile strikes reportedly hit Ukraine's capital Kyiv and other cities on Saturday, as Moscow said its troops had seized the urban area of Mariupol and only a small contingent of Ukrainian fighters remained inside a steelworks in the besieged southern port, according to reports by Reuters.

Russia's claim to have all but taken control of Mariupol, scene of the war's heaviest fighting and worst humanitarian catastrophe, could not be independently verified. It would be the first major city to have fallen to Russian forces since the Feb. 24 invasion.

Explosions were also reported in Ukraine's capital Kyiv and the western city of Lviv on Saturday morning, prompting concerns that Russia stepped up attacks on Ukraine in retaliation for the sinking of its flagship missile cruiser Moskva by Ukrainian forces.

Russia said that it had destroyed production buildings of an armored vehicle plant in Kyiv and a military repair facility in the city of Mykolaiv, the Interfax news agency quoted Russia's defence ministry as saying on Saturday.

Separately, Reuters reported that the head of Russia's navy met with sailors from Moskva, the Russian Black Sea flagship that sank on Thursday.

A senior U.S. Defense official told NBC News that the Pentagon now believes Ukraine's claims that it sank the Moskva.

Moskva crew members meet with Russian navy boss

The head of the Russian navy met with crew members from the sunken Moskva missile cruiser on Saturday, Reuters reported, citing Russia's defense ministry.

Admiral Nikolai Yevmeno was shown in a short ministry video reviewing about 100 sailors, Reuters said. Russia claimed this week that the entire crew of the Moskva, which had a crew of about 500, survived the ship's destruction.

Russia's Black Sea flagship Moskva sank after it was struck by two Ukrainian Neptune missiles, the Pentagon now believes. Ukraine said earlier this week that it hit the Moskva with missiles; Russia then said that the ship was the victim of an ammunition explosion.

The Moskva was the Russians' command vessel in the region and the primary ship for anti-air defense. A senior Defense official told NBC News that it's unclear why the Moskva's air defense systems didn't work against Ukraine's missiles.

Low-flying cruise missiles can be more difficult to spot on radar during stormy seas. The Russian defense ministry told Russia's state-controlled media that the Moskva went down as it was being towed back to port "in a storm."

Russia's defense ministry said that the Moskva's sailors will continue their service with the navy.

— Ted Kemp

Zelenskyy says Mariupol's fate is key to peace talks

Ukrainian President Volodymyr Zelenskyy told Ukrainian media that the continuing siege of Mariupol could scuttle any attempts to find a negotiated end to the war.

"The destruction of all our guys in Mariupol – what they are doing now – can put an end to any format of negotiations," Zelenskyy said in an interview.

Zelenskyy also said he spoke with the leaders of Britain and Sweden about how best to help those defending Mariupol and the tens of thousands of civilians trapped there.

Mariupol's fate can be decided either through battle or diplomacy, he said.

"Either our partners give Ukraine all of the necessary heavy weapons, the planes, and without exaggeration immediately, so we can reduce the pressure of the occupiers on Mariupol and break the blockade," he said in his nightly video address to the nation. "Or we do so through negotiations, in which the role of our partners should be decisive."

Zelenskyy said the situation in Mariupol remains "inhuman" and that Russia "is deliberately trying to destroy everyone who is there."

The president's office said the southern port city is holding out but the situation is critical. The battle for Mariupol has come at a horrific cost to trapped and starving civilians. Locals reported seeing Russian troops digging up bodies from residential courtyards and prohibiting new burials. It was unclear why.

Russian Defense Ministry spokesman Igor Konashenkov said Saturday that Ukrainian forces have been driven out of most of the city and remain only in the huge Azovstal steel mill.

Mariupol's capture would allow Russian forces from the Crimean Peninsula to fully link up with troops in the Donbas region, Ukraine's eastern industrial heartland.

— Associated Press

Russia says its forces take most of Mariupol

Russia says it has seized the urban area of Mariupol and only a small contingent of Ukrainian fighters remain inside the steelworks in the besieged southern port, according to a report from Reuters. It would be the first major city to have fallen to Russian forces since the Feb. 24 invasion.

"The situation is very difficult" in Mariupol, President Volodymyr Zelenskyy told the Ukrainska Pravda news portal. "Our soldiers are blocked, the wounded are blocked. There is a humanitarian crisis ... Nevertheless, the guys are defending themselves."

Mariupol is the main port of the Donbas, a region of two provinces in the southeast which Moscow demands be fully ceded to separatists.

Ukraine says it has so far held off Russian advances elsewhere in the Donbas regions of Donetsk and Luhansk, where at least one person was killed in shelling overnight.

— Sarah Whitten

Russian Maj. Gen. Vladimir Frolov has died in Ukraine

Russian general Vladimir Frolov has died in Ukraine, according to a statement from Alexander Beglov, the governor of St. Petersburg. At least seven other Russian generals have died since the war began.

Frolov, deputy commander of the 8th Guards Army in east Ukraine, died in battle, according to a report published by the New York Times. No details were given about when or where he died. He was buried in St. Petersburg on Saturday. 

He became the 42nd high-ranking officer known to have died in a war, according to news reports.

— Sarah Whitten

Ukraine team gets ovation at Invictus Games

The Invictus Games for injured and ill service personnel and veterans has opened with a standing ovation and a tribute from Prince Harry for Ukrainian team members who left their war-torn nation to compete.

With Harry and his wife, Meghan, in the front row for the opening ceremony Saturday night, competitors cheered for nearly a minute as the Ukrainian team waved their nation's blue-and-yellow flag after Dutch Prime Minister Mark Rutte welcomed them.

The event that was delayed by two years because of the coronavirus pandemic.

Prince Harry founded the Invictus Games to aid the rehabilitation of injured or sick military service members and veterans, by giving them the challenge of competing in sports events similar to the Paralympics. Welcoming all competitors, Harry singled out the 19-strong Ukrainian team and their supporters.

"Your bravery in choosing to come and for being here tonight cannot be overstated," he said, a day after meeting the Ukrainians at a reception.

"You know, we stand with you. The world is united with you. And still you deserve more. And my hope is that these events, this event, creates the opportunity ... of how we as a global community can better show up for you," Harry added.

— Associated Press

Ukraine claims more than 20,000 Russian military dead

Editor's note: This post contains a picture of Russian casualties.

Ukraine's defense agency claimed that about 20,100 Russian military personnel have been killed during its invasion on the Eastern European country.

In addition to the claimed deaths, the agency said Russia has lost more than 163 aircraft, 762 tanks, 1,982 armored personnel vehicles and 66 anti-aircraft warfare systems since the full-scale invasion began on Feb. 24.

Intelligence on Russian deaths have widely varied and been extremely difficult to calculate. But the large toll would represent a stunning loss for Russia, which expected a rapid takeover of the country. For comparison, the Soviet Union lost around 15,000 troops during its war in Afghanistan from 1979 to 1989.

Just over three weeks ago, NATO estimated 7,000 to 15,000 Russians were killed in the invasion. Moscow hasn't given an update around casualties since last month, when it reported 1,351 troops had died in the war.

— Jessica Bursztynsky

Russian forces shell oil refinery in Lysychansk

Russian forces shelled an oil refinery in the Ukrainian city of Lysychansk and a large fire erupted, according to Luhansk Regional Governor Serhiy Haidai.

Haidai said it was not the first time the refinery has been targeted and accused the Russians of trying to "exhaust" local emergency services. He noted that there was no fuel at the refinery at the time of the attack.

Ukraine's presidential office said that missile strikes and shelling over the past 24 hours have occurred in eight regions: Donetsk, Luhansk and Kharkiv in the east, Dnipropetrovsk, Poltava and Kirovohrad in the central Ukraine and Mykolaiv and Kherson in the south.

The head of regional legislature, Hanna Zamazeyeva, said the targets included several residential blocks "where there are no military facilities."

— Sarah Whitten

One dead, several wounded in morning airstrikes, Kyiv mayor reports

Kyiv Mayor Vitali Klitschko said one person is dead and several more were wounded in early morning airstrikes on the Darnytski district of the capital.

The Russian Defense Ministry said the attacks targeted an armored vehicle plant in the Ukrainian capital.

Klitschko urged Ukrainians not to return to the capital, warning that strikes on city will likely continue and its suburbs are rigged with explosives. Because of the mines, Kyiv residents are barred from visiting parks and forests in the northeastern areas that border with liberated territories formerly occupied by Rusisans.

— Sarah Whitten

Russia's Putin, Saudi Crown Prince bin Salman discuss Ukraine, OPEC+

Russian President Vladimir Putin spoke with Saudi Crown Prince Mohammad bin Salman on Saturday, their second call since the start of Russia's invasion of Ukraine. The Saudi Press Agency said the two discussed bilateral relations and "ways of enhancing them in all fields."

The Saudi readout of the call said the crown prince affirmed support for efforts that would lead to a political solution to the crisis in Ukraine. The kingdom recently announced $10 million in humanitarian aid for Ukrainian refugees.

The Kremlin's statement added the two also discussed the ongoing conflict in Yemen, where a Saudi-led coalition has been at war for years, as well as their joint work on an oil output agreement, known as OPEC+. The oil pact has kept a cautious lid on production by major producers, supporting oil prices.

Ukraine has urged nations around the world to cut their dependency on Russian oil imports that it says finance Russia's military war on Ukraine.

— Associated Press

Italy bars all Russian ships from its ports

Italy is barring all Russian ships from its ports starting Sunday, as part of expanded EU sanctions announced earlier this month. Ships already in Italian ports must leave immediately "after completing their commercial activity,″ according to a notice sent to port authorities throughout the country.

— Associated Press

Charitable donations to Ukraine have reached nearly $924 million

Donations into Ukraine have reached nearly $924 million, according to a statement from President Volodymyr Zelenskyy's administration.

The bulk of donations comes from the United Kingdom, accounting for 47% of the funds. Philanthropists in the Netherlands contributed almost 18%, while the U.S. made up almost 8% of the total funds. Donors in the Czech Republic contributed 11%.

Andriy Yermak, the head of the president's office, said in a statement the funds are mostly going to the United Nations and international humanitarian organizations. Those then help in aiding refugees across Europe. More than 4.8 million Ukrainians have fled the country since the start of the war, according to data from the UN.

— Jessica Bursztynsky

Ukraine has 'no trust' in Russian Mariupol negotiators

Ukrainian President Volodymyr Zelenskyy said he's distrustful of Russian negotiators when it comes to the besieged city of Mariupol.

"To be honest, there is no trust in the negotiators on Mariupol," Zelenskyy said in an interview with a Ukrainian media outlet, according to an NBC translation. "We agreed that there would be humanitarian corridors. We wanted to take away the wounded, our women and children, but Russia refused."

Mariupol has been a scene of intense fighting, with refugees who are fleeing describing increasingly dire circumstances.

"Our military is blocked, the wounded are blocked. There is a humanitarian crisis, there is no food, no water, no medicine. Nevertheless, the guys are defending themselves. And only 'thank you' is not enough, so negotiations are underway," Zelenskyy said.

— Jessica Bursztynsky

How the war is cutting into auto production

Auto industry watchers are slashing production and sales forecasts for the next two years, due to the ongoing war between Russia and Ukraine, CNBC's Robert Ferris reports.

Factories have shuttered in Eastern Europe, leading to a spike in prices of already precious raw materials, such as palladium and nickel. Watch the video to learn more on how the war is cutting into auto production.

— Annie Nova

UK remains 'resolute' in supporting Ukraine after Russia bars some leaders

A British government spokesperson responded to Russia's barring entry of certain U.K. officials, saying the nation was "resolute" in supporting Ukraine.

"The UK and our international partners stand united in condemning the Russian government's reprehensible actions in Ukraine and calling for the Kremlin to stop the war," the spokesperson said in response to the Kremlin barring the nation's top leaders, according to Reuters. "We remain resolute in our support for Ukraine."

The move from the Kremlin comes after British Prime Minister Boris Johnson visited Kyiv and met with Ukrainian President Volodymr Zelenskyy. The nation has also continuously increased its sanctions on Russia and its key figures.

— Jessica Bursztynsky

Ukrainian Railways limit exports of some food staples

Ukraine's state-owned railway company has temporarily restricted the transportation of some agricultural goods through border crossings to Poland and Romania, consultancy APK-Inform said on Saturday.

It gave no reason for the restrictions.

Ukraine, a major agricultural producer, used to export most of its goods through seaports but since Russia's invasion has been forced to export by train via its western border.

APK-Inform said restrictions on the movement of goods to Poland through Yahodyn have been put in place from April 16 to April 18.

There are also restrictions on the transportation of cereals, oilseeds, grains and other food products through Izov to the Polish towns of Hrubeszew and Slawkov.

From April 16 until further notice, there are restrictions on the export of grain and seeds to Romania through the Dyakovo and Vadul-Siret crossings, the consultancy said.

The railway company was not available for immediate comment.

— Reuters

Russian military campaign could go into next phase in days

Russian troops may start the next phase of the Kremlin's military campaign in the next few days, NBC News reported.

U.S. intelligence believes the Russian military could start moving some forces back into Ukraine as soon as this weekend or early next week, NBC News reported, citing two unnamed senior U.S. defense officials.

Russian forces had retreated from around Kyiv and northern Ukraine. Officials at the time expected troops to regroup and begin an offensive on the Donbas region and southeastern Ukraine. Now, though, the Russian military could move troops back into Ukraine before all of its troops are ready to fight again, NBC News reported.

— Jessica Bursztynsky

Ukraine's richest man vows to rebuild besieged Mariupol

Ukraine's richest man has pledged to help rebuild the besieged city of Mariupol, a place close to his heart where he owns two vast steelworks that he says will once again compete globally.

Rinat Akhmetov has seen his business empire shattered by eight years of fighting in Ukraine's east but remains defiant, sure that what he calls "our brave soldiers" will defend the Sea of Azov city reduced to a wasteland by seven weeks of bombardment.

For now, though, his Metinvest company, Ukraine's biggest steelmaker, has announced it cannot deliver its supply contracts and while his financial and industrial SCM Group is servicing its debt obligations, his private power producer DTEK "has optimized payment of its debts" in an agreement with creditors.

"Mariupol is a global tragedy and a global example of heroism. For me, Mariupol has been and will always be a Ukrainian city," Akhmetov said in written answers to questions from Reuters.

"I believe that our brave soldiers will defend the city, though I understand how difficult and hard it is for them," he said, adding he was in daily contact with the Metinvest managers who run the Azovstal and Illich Iron and Steel Works plants in Mariupol.

— Reuters

Moscow bars UK politicians from entering Russia

Russia's foreign ministry said on Saturday that it had barred entry to the country for British Prime Minister Boris Johnson, Foreign Secretary Liz Truss, Defence Secretary Ben Wallace and 10 other British government members and politicians, Reuters reported.

The move was taken "in view of the unprecedented hostile action by the British Government, in particular the imposition of sanctions against senior Russian officials," the ministry said in a statement, adding that it would expand the list soon.

— Reuters

Russia reportedly strikes armored vehicle plant, military repair facility

Russia says that it has destroyed production buildings of an armored vehicle plant in Kyiv and a military repair facility in the city of Mykolaiv, the Interfax news agency quoted Russia's defence ministry as saying on Saturday.

Russian Defense Ministry Igor Konashenkov said that Russia had used high-precision long-range weapons to carry out the strikes.

Konashenkov also stating that a Ukrainian Su-25 aircraft was shot down by Russian air defense systems near the village of Izyum.

— Holly Ellyatt

Explosions heard in Kyiv and Lviv, officials say

Explosions were heard in the early hours on Saturday in Ukraine's capital, Kyiv, and the western city of Lviv, according to local officials.

Kyiv's Mayor Vitali Klitschko said on the Telegram messaging app that Kyiv "came under fire" this morning with explosions heard in the Darnytskyi district on the outskirts of the city.

Rescuers and medics are currently working on the site, he said, and there was no information on the number of casualties from the blasts.

Explosions have also been heard in Lviv in western Ukraine this morning. On Telegram, Governor Maksym Kozytskyi said an air raid had taken place between 05:46 and 07:02 local time.

— Holly Ellyatt

Damaged roads in Ukraine hindering humanitarian aid, UK’s Defence Ministry says

Ukraine's roads and other infrastructure have been badly damaged by Russian troops, and that is now posing a significant challenge in delivering humanitarian aid to some areas, said the U.K.'s Defence Ministry in its daily intelligence update.

"Road infrastructure in conflict affected areas of Ukraine has sustained significant damage. Russian troops have exacerbated this by destroying bridges, employing land mines and abandoning vehicles along key routes as they withdrew from northern Ukraine," the ministry said in its update, posted on Twitter.

River crossings in and around the northern Ukrainian city of Chernihiv have been destroyed, leaving only one pedestrian bridge in the city, the update said.

"Damage to Ukraine's transport infrastructure now presents a significant challenge in delivering humanitarian aid to areas formerly besieged by Russia," the ministry tweeted.

— Weizhen Tan

Zelenskyy appeals for ‘stronger, more destructive’ sanctions

Ukrainian President Volodymyr Zelenskyy says he's been hearing different predictions about how long the war with Russia will last.

"Some say a few weeks. Others — several years. Some say the war will last until the end of this year. And someone advises to prepare for a permanent confrontation with Russia as long as it exists," he said in his nightly address to the nation.

But Zelenskyy says the "effectiveness of instruments of influence" on Russia used by Ukraine as well as its entire anti-war coalition against Russia must be taken into account, when predicting how long the war will last.

"The success of our military on the battlefield is really significant. Historically significant. But not enough to clean our land from the occupiers yet. We'll beat them more," he said.

"Sanctions against Russia are very significant. Economically painful. But still not enough for the Russian military machine to be left without means of subsistence. We promote stronger, more destructive ones," Zelenskyy said.

These two areas, he says, will determine how long this war will last. The amount of support for Ukraine "literally defines how many more Ukrainians the occupiers will manage to kill."

"If someone says: year or years, I answer: you can make the war much shorter. The more and the sooner we get all the weapons we have requested, the stronger our position will be and the sooner peace will come," he said. "The sooner the democratic world recognizes that the oil embargo against Russia and the complete blockade of its banking sector are necessary steps towards peace, the sooner the war will end."

— Weizhen Tan

Read CNBC's previous live coverage here:

Zelenskyy appeals for 'stronger, more destructive' sanctions, says up to 3,000 Ukrainian soldiers are dead