A Chinese defense spokesperson on Thursday urged the U.S. side to exercise caution on the Taiwan question and the South China Sea issue.

Zhang Xiaogang, spokesperson for the Ministry of National Defense, made the remarks in response to a media query regarding a U.S. warship illegally intruding into waters adjacent to Ren'ai Jiao, part of China's Nansha Qundao in the South China Sea, and a U.S. patrol aircraft recently flying over the Taiwan Strait.

Zhang noted that China holds indisputable sovereignty over the Nansha Qundao, including Ren'ai Jiao, and the adjacent waters.

The U.S. warship illegally intruded into the waters adjacent to Ren'ai Jiao without authorization from the Chinese government, seriously damaging China's sovereignty and security, violating international law and basic norms governing international relations, and undermining regional peace and stability, Zhang said.

He stressed that China always respects the navigation and overflight rights of all countries in the South China Sea following international law but firmly opposes any action that endangers China's sovereignty and security in the name of freedom of navigation and overflight.

When commenting on the U.S. side's recent move over the Taiwan Strait, Zhang said that Taiwan is an integral part of China's territory and that the U.S. should never attempt to challenge China's firm determination to defend its national sovereignty and territorial integrity at any time.

The waters of the Taiwan Strait are divided into internal waters, territorial sea, contiguous zone, and exclusive economic zone, following the United Nations Convention on the Law of the Sea and China's domestic law, and the so-called "international waters" do not exist at all, he said.

The spokesperson emphasized that there is no such thing as "international waters" in international maritime law.

"By claiming that the Taiwan Strait is 'international waters,' the United States is creating an excuse to manipulate the Taiwan question and threaten China's sovereignty and security. China is firmly opposed to this," Zhang added.

The spokesperson stated that China again urges the United States to act cautiously on the Taiwan question and the South China Sea issue and cease provocations.