This was CNBC's live blog tracking developments on the war in Ukraine.

Ukraine sent reserve units to the border areas of the northeastern Kharkiv region, seeking to shore up its defenses against intensifying Russian attacks.

Ukraine's Defense Ministry said in a Google-translated post via Telegram that Russian forces sought to break through Ukraine's defense line in Kharkiv at approximately 5 a.m. local time, but were beaten back.

Oleh Syniehubov, head of Ukraine's Kharkiv region, said that "the armed forces of Ukraine confidently hold their positions" and "not a single meter has been lost."

In a separate post, Syniehubov said that "massive" Russian shelling in the Kharkiv region had killed at least two people and injured five others.

Russian attacks in eastern Ukraine have intensified in recent weeks, which analysts say likely reflects the Kremlin's intent to secure tactical gains before the arrival of Western military aid to the front lines.

Ukraine attacked an oil refinery in Russia's Kaluga region in the early hours of Friday, setting the facility on fire, according to Russian media reports.

Vladislav Shapsha, governor of the Kaluga region, said via Telegram that the fire was promptly extinguished, and the extent of the damage was still being assessed. He did not say at what facility the incident took place.

Moscow mayor Sergey Sobyanin said on Friday that Russia's Defense Ministry intercepted a Ukrainian drone flying toward the Russian capital, with preliminary information indicating no damage or casualties at the crash site.

U.S. to announce new $400 million military aid package for Ukraine, official says

The United States is preparing a $400 million military aid package for Ukraine, as the U.S. returns to a regular pace of supplying weapons to Ukraine following the passage of a $95 billion bill, a U.S. official told Reuters on Friday.

The Ukraine aid package includes artillery, munitions for NASAMS air defenses, anti-tank munitions, armored vehicles and small arms that can immediately be put to use on the battlefield, the official said, speaking on condition of anonymity.

-Reuters

Russian forces advance one kilometer near Ukraine's Vovchansk, Kyiv military source says

Russian forces have advanced one kilometer (0.62 mile) into Ukraine's northeast Kharkiv region near Vovchansk, a high-ranking Ukrainian military source said on Friday.

The source said the Russian military was aiming to advance as much as 10 kilometers into the region in an effort to establish a buffer zone. Ukrainian forces were fighting to hold back Moscow's advance.

-Reuters

Two killed, five injured in Russian shelling of Ukraine's Kharkiv region

Russian shelling in Ukraine's northeastern Kharkiv region killed at least two people and injured five others, according to an update from the regional governor.

Oleh Syniehubov, head of Ukraine's Kharkiv region, said in a Google-translated post on Telegram that the border communities of the Kharkiv region were under intensified and "massive" shelling from Russian forces.

CNBC could not independently verify the report.

— Sam Meredith

Zelenskyy says Ukraine was prepared for Russia's ground assault in the Kharkiv region

Ukrainian President Volodymyr Zelenskyy on Friday said the country's forces were ready for Russia's latest ground assault on the border of the northeastern Kharkiv region.

"Ukraine met them there with troops: brigades and artillery," Zelenskyy said at a news conference, according to Reuters.

His comments come as Ukrainian forces seek to hold their positions amid a fresh push from Russian forces. Ukraine's Defense Ministry said on Friday that it had directed reinforcements to the Kharkiv region to shore up its defenses.

Analysts say intensifying Russian attacks in eastern Ukraine likely reflects the Kremlin's intent to secure tactical gains before the arrival of Western military aid to the front lines.

— Sam Meredith

Russia says it has taken full control of villages in Kharkiv and Donetsk

Russia's Defense Ministry on Friday said it had captured two villages in the northeastern region of Kharkiv and one village in the eastern Donetsk region.

The ministry said it had taken "full control" of the villages of Kotlyarovka and Kislovka in the Kharkiv region and Novokalinovo in the Donetsk region.

It comes as Russian forces intensify their ground attacks on the border areas of Kharkiv region.

The city of Kharkiv, which is thought to be particularly vulnerable given its proximity to Russia, has been devastated by a barrage of air strikes in recent months.

— Sam Meredith

Ukraine sends reserve units to help defend the Kharkiv region from Russian attacks

Ukraine's Defense Ministry said on Friday that reserve units had been sent to the northeastern region of Kharkiv to repel Russian forces.

The ministry said in a Google-translated post via Telegram that Russian forces sought to break through Ukraine's defense line in Kharkiv at approximately 5 a.m. local time, but were beaten back.

"To strengthen the defense in this part of the front, reserve units have been sent. The defense forces of Ukraine continue to hold back the enemy's offensive," it added.

CNBC could not independently verify the report.

— Sam Meredith

Russia's Victory Day military parade was 'reduced in scale' compared to pre-war events, UK says

Russia's 79th "Victory Day" military parade was "reduced in scale" compared to events held prior to the country's full-scale invasion of Ukraine, according to Britain's Ministry of Defense.

Russia held the annual event on Thursday in Moscow to commemorate the Soviet Union's victory over Nazi Germany in World War II.

The U.K.'s MoD said on Friday in its latest intelligence update that Victory Day parades were canceled in 24 Russian cities, primarily those that border Ukraine, "likely due to poor security." This compares to 21 canceled parades last year, the ministry said.

"Although the fly-past was reinstated … the Moscow parade was reduced in scale with less modern military equipment on display when compared to pre-war parades," the ministry said via social media platform X.

— Sam Meredith

Russian forces intensified shelling of Ukraine's Kharkiv region and tried to break through border, governor says

Russian forces unsuccessfully tried to break through the border into Ukraine with sabotage groups and ratcheted up shelling of the Vovchansk town in Ukraine's Kharkiv region, according to the city's governor.

Oleh Syniehubov, head of Ukraine's Kharkiv region, said in a Google-translated post via Telegram on Friday that "the armed forces of Ukraine confidently hold their positions" and "not a single meter has been lost."

He characterized Russia's border actions as "provocations" and said Russia's armed forces do not pose a threat to Kharkiv.

CNBC could not independently verify the report.

— Sam Meredith

Ukrainian drone intercepted over Moscow region, mayor says

Moscow mayor Sergey Sobyanin said on Friday that Russia's Defense Ministry intercepted a Ukrainian drone flying toward the Russian capital, with preliminary information indicating no damage or casualties at the crash site.

"In the urban district of Podolsk, air defense units of the Ministry of Defense repelled an attack by a drone flying towards Moscow," Sobyanin said in a Google-translated post on Telegram.

"Preliminary data suggests that there was no damage or casualties at the crash site of the debris. Emergency services are working at the scene," he added.

CNBC could not independently verify the report.

— Sam Meredith

Russia ramps up ground attacks in eastern Ukraine ahead of the arrival of Western military aid

The rate of Russian ground attacks in eastern Ukraine has "markedly increased" in recent weeks, according to analysts at the Institute for the Study of War (ISW) think tank.

It likely reflects current battlefield conditions and the Kremlin's desire to secure tactical gains before the arrival of Western military aid to the front lines, according to the ISW's latest assessment of Russia's full-scale invasion of Ukraine.

Britain's Ministry of Defense said on Thursday that Russian attacks in eastern Ukraine intensified in April, rising by 17% from the month prior. Of these attacks, the ministry said more than three-quarters were in the front-line areas of Avdiivka, Chasiv Yar and Marinka.

Analysts at ISW said they expect Russian forces to maintain a high rate of attacks across eastern Ukraine "in order to make gains before the arrival of Western aid in Ukraine."

Once the aid arrives to front-line areas, ISW analysts said this will likely stymie Russia's ability to continue the high rate of attacks and the pursuit of more gains.

— Sam Meredith

Two injured as residential houses set ablaze by Russian attack on Kharkiv, Ukraine says

Two people were injured and three residential buildings were consumed by fire as a result of Russia's overnight attack on Ukraine's Kharkiv, according to the city's regional governor.

Oleh Syniehubov, head of Ukraine's Kharkiv region, said in a Google-translated post on Telegram that a fire broke out at three houses in the early hours of Friday.

Two people, an 11-year-old and a 72-year-old, were said to have been shell-shocked by the attack and were receiving medical support.

Syniehubov shared photos on Telegram of what appeared to be the aftermath of the attack, which showed buildings on fire and black smoke billowing into the night sky.

CNBC could not independently verify the report.

— Sam Meredith

Ukraine drone attack sparks fire at an oil refinery in Russia's Kaluga region

A Ukrainian drone attack set an oil refinery in Russia's Kaluga region on fire, according to Russian media reports.

Several powerful explosions were heard in the Dzerzhinsky district of the Kaluga region early on Friday, according to The Moscow Times, citing Russian Telegram channel SHOT.

Vladislav Shapsha, governor of the Kaluga region, said in a Google-translated post via Telegram that the fire was swiftly extinguished by emergency workers and the extent of the damage was being assessed.

Preliminary data indicated no one was killed in the attack, Shapsha said. He did not specify at what facility the incident took place.

Anton Gerashchenko, a former advisor to Ukraine's Ministry of Internal Affairs, said via social media platform X on Friday that the oil refinery is the largest in Russia's Kaluga region and the main complex for processing commercial oil and gas condensate.

CNBC could not independently verify the reports. Russia has launched a barrage of attacks on Ukraine's energy infrastructure in recent months, drawing retaliatory attacks on refineries by Kyiv.

— Sam Meredith

Ukraine's Parliament votes in favor of bill that cracks down on draft dodgers

The Ukrainian Parliament on Thursday voted in favor of a bill that aims to crack down on Ukrainians dodging being drafted to the country's armed forces, Reuters reported.

Fines for anyone trying to avoid being called up to fight would be increased and authorities would be allowed to detain draft dodgers for up to three days under the new bill.

The bill was backed by a majority of lawmakers, but still needs to be signed into law by Ukrainian President Volodymyr Zelenskyy.

This comes as Ukraine has been struggling with a shortage of soldiers, which has prompted the government to come up with various new ways to expand its army's manpower. Earlier in the week the Ukrainian Parliament passed a bill allowing some prisoners to enlist.

A new mobilization law is also due to come into effect, which lowers the minimum age for army recruits among other provisions.

— Sophie Kiderlin

Russia and Belarus to carry out joint tactical nuclear weapons drills, Putin says

Russia and Belarus will join forces to carry out tactical nuclear weapons drills, Russian President Vladimir Putin said on Thursday.

"Since non-strategic nuclear weapons are stationed on the territory of Belarus, this time we invited our friends, allies, and the President of Belarus [Alexander Lukashenko] asked for this, to take part in one of the stages of this exercise. We conduct them regularly," Putin said, according the Interfax news agency.

Non-strategic — or tactical — nuclear weapons are designed for use in battlefield situations as opposed to their larger and more destructive counterparts, strategic nuclear weapons, which could destroy entire cities.

Russia and its neighbor and ally Belarus had both announced their intentions earlier this week to carry out their own drills.

Russia has stationed tactical nuclear weapons in Belarus but retains control over the weapons. Russia said its decision to station such hardware in Belarus was no different to the U.S.' positioning of non-strategic nuclear weapons in Europe.

— Holly Ellyatt

Read CNBC's previous live coverage here:

Putin says Russia 'will not allow anyone to threaten us' as Moscow revels in military might