Beijing: China urged the US to respect and abide by its laws, and not to undermine the mutual trust and regional peace and stability.
Foreign Ministry spokesperson Hua Chunying on Saturday made the remarks as reports said a US Navy guided-missile destroyer sailed within 12 nautical miles of Zhongjian Dao, Xisha Islands, Xinhua reported.
According to China's law on the territorial sea and contiguous zone enacted in 1992, foreign warships entering China's territorial waters must be approved by the Chinese government.
"The US warship violated Chinese law and entered the country's territorial sea without authorisation. The Chinese side conducted surveillance and vocal warnings to the US warship," Hua said.
Defence Ministry spokesman Yang Yujun also said the US act severely violated Chinese law, sabotaged the peace, security and good order of the waters, and undermined the region's peace and stability. The Defence Ministry is firmly against this, he said.
Yang said China's law on the territorial sea and contiguous zone accords with the international law and practice, and that many other countries have similar laws.
The Chinese government also issued a statement on territorial sea baseline on May 15, 1996, which announced part of the baseline of the territorial sea adjacent to China's mainland and the baseline of the territorial sea adjacent to the Xisha Islands.
"The US side is fully aware of this, yet it still sent its warship into China's territorial sea without authorisation. It is a deliberate provocation," Yang said.
According to Yang, Chinese troops on the islands and Navy vessels and warplanes took actions immediately. They identified and verified the US warship, warned and expelled it swiftly.
For many years, the US side has proposed measures to ensure navigation safety of ships and aircraft of all parties, but it repeatedly sent vessels and planes into China's territorial sea and air space regardless of the country's opposition, leading to close encounters of navy and air force troops of the two countries, Yang said.
He added that the move on the US side is very unprofessional and irresponsible for the safety of the troops of both sides, and may cause extremely dangerous consequences.
The Chinese armed forces will take whatever measures necessary to safeguard China's sovereignty and security, no matter what provocations the US side may take, Yang said.