China is in dispute with several of its neighbours over claims of territorial waters in South China Sea
China's military on Monday said a US combat ship illegally entered waters adjacent to the Second Thomas Shoal, a disputed South China Sea atoll.
"The US seriously undermined regional peace and stability," said a spokesperson for China's Southern Theater of Operations in a statement.
The spokesperson also said the US deliberately disrupted the South China Sea and seriously violated China's sovereignty.
China is in dispute with several of its neighbours over its extensive claims of territorial waters in the South China Sea.
In recent months it has had several confrontations with Philippine vessels, and also protested about US ships patrolling the disputed areas.
The spokesperson said the Chinese People's Liberation Army organized maritime troops to follow and monitor the US ship., and that "its troops in the theater are on high alert at all times to resolutely defend national sovereignty."
On Sunday, the Philippine Coast Guard deployed two of its vessels in the South China Sea after monitoring an "alarming" increase in the number of Chinese maritime militia vessels at a reef within the country's exclusive economic zone.
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