China has formally registered its objections to a statement issued at an unprecedented summit involving leaders from the United States, South Korea, and Japan, in which they condemned China's "aggressive behavior".

The summit, hosted by US President Joe Biden at Camp David, marks the initiation of a new phase of close security cooperation among the three nations against China.

On Friday, the leaders expressed their joint opposition to China's "dangerous and aggressive behavior" in the maritime disputes surrounding the East and South China seas.

Beijing responded on Monday, denouncing the leaders for their criticism of China on issues related to Taiwan and maritime affairs.

The Chinese Foreign Ministry Spokesperson Wang Wenbin said the leaders' statement amounted to an unwarranted interference in China's internal matters and an attempt to sow discord between China and its neighboring countries.

Wang underscored China's "strong dissatisfaction and firm opposition" to the statement and confirmed that the country had formally lodged its protest with relevant parties.

The Camp David joint statement specifically addressed Taiwan, emphasizing that maintaining peace and stability concerning the island is integral to global security and prosperity. The statement reiterated the leaders' commitment to a peaceful resolution of cross-strait issues while claiming to uphold the One-China principle.

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China's People's Liberation Army conducted air and sea exercises around Taiwan on Saturday, which it characterized as a "stern warning" following the visit of Taiwan's vice president to the United States.

Foreign Ministry Spokesperson Wang urged countries concerned about stability in the Taiwan Strait to adhere to the One-China principle, cease endorsing or supporting advocates of Taiwan independence, and take concrete actions to safeguard regional peace and stability. Wang firmly asserted that the Taiwan question remains a purely internal matter for China.

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In the same press conference, the Chinese Foreign Ministry Spokesperson Wang Wenbin announced that commercial flights between Beijing and Pyongyang would be restored. 

He also announced that China would endorse flight plans for routes between Beijing and Pyongyang operated by the Korean state-run airline Air Koryo. 

This move signals a resumption of air connectivity between the two nations after the DPRK decided to close its borders back in 2020.