• Chinese President Xi Jinping pledged a "complete reunification" with Taiwan — drawing a strong rebuke from the democratic, self-ruled island.
• Taiwan's Mainland Affairs Council acknowledged that the Chinese Communist Party had achieved economic development, but added that it has clamped down on democracy, violated human rights and grown more dictatorial.
• The council said the Taiwanese government remains determined to defend the island's sovereignty and democracy, while urging Beijing to abandon military intimidation toward the island.

Chinese President Xi Jinping on Thursday pledged a "complete reunification" with Taiwan — drawing a strong rebuke from the democratic, self-ruled island, which criticized the Chinese Communist Party's "dictatorship."

Taiwan and mainland China are separated by the Taiwan Strait, which is only about 100 miles wide (160 km) at its narrowest point. The ruling Chinese Communist Party in Beijing has never controlled Taiwan, but it claims the island is a runaway province that must one day be reunited with the mainland — by force if necessary.

In a speech to mark the CCP's 100th year, Xi called "reunification" with Taiwan an "unswerving historical mission" of the party and a "common aspiration" of the Chinese people. The audience erupted in applause in response.

Taiwan's Mainland Affairs Council lashed out at the CCP in a statement after Xi's speech. It said the party had achieved economic development in China, but added that it has clamped down on democracy, violated human rights and grown more dictatorial domestically.

"Democracy, freedom, human rights and the rule of law are core principles of Taiwanese society — a major institutional difference from the other side of the strait," said the Mandarin-language statement, which was translated by CNBC.

The council said the Taiwanese government remains determined to defend the island's sovereignty and democracy. It added that the Taiwanese people have long rejected the "one China principle" and urged Beijing to abandon military intimidation directed at the island.

The "one China principle" refers to the concept that there's only one central Chinese government — the one under the Communist Party in Beijing.

Under Xi's leadership, China has more aggressively asserted its claims over Taiwan, and there have been numerous breaches of Taiwan's air defense zone by Chinese warplanes this year.

Taiwan has also become a contentious issue between the United States and China. The U.S. has in recent years moved closer to Taiwan — angering Beijing, which considers the island to have no rights to conduct its own diplomacy.

China pressures other countries and international organizations not to deal with Taiwan independently. In May, the G-7 group of advanced economies, including the United States, called for Taiwan to be allowed to participate in forums put on by the World Health Organization.

A former senior diplomat from Singapore, Bilahari Kausikan, told CNBC on Wednesday that Taiwan is the most dangerous flashpoint in U.S.-China relations.