China has strongly condemned the United States after an American warship deliberately sailed near one of its islands in the hotly-contested South China Sea to exercise freedom of navigation and challenge Beijing's vast territorial claims.
The missile destroyer USS Curtis Wilbur sailed within 12 nautical miles of Triton Island in the Paracel chain "to challenge excessive maritime claims of parties that claim the Paracel Islands", without notifying the three claimants beforehand, defence department spokesman Mark Wright said in Washington.
China, Taiwan and Vietnam have overlapping claims in the Paracels and require prior notice from ships transiting what they consider their territorial waters.
The latest operation was particularly aimed at China, which has increased tensions with the US and its south-east Asian neighbours by embarking on massive construction of man-made islands and airstrips in contested areas.
In October, another US warship sailed in the nearby Spratly Islands near Subi Reef, where China has built one of seven artificial islands.
Mr Wright said the attempts to restrict navigational rights by requiring prior notice were inconsistent with international law. US officials said such ship movements would be regular in the future.
China responded swiftly, with defence ministry spokesman Yang Yujun saying the US action "severely violated Chinese law, sabotaged the peace, security and good order of the waters, and undermined the region' s peace and stability".
According to Yang, Chinese troops on the island and navy vessels and warplanes took actions immediately, identified the US warship and "warned and expelled it swiftly."
He said the US operation was "very unprofessional and irresponsible for the safety of the troops of both sides, and may cause extremely dangerous consequences".
Chinese armed forces would take whatever measures "necessary to safeguard China's sovereignty and security, no matter what provocations the US side may take", he added.
Foreign ministry spokesman Hua Chunying said the Chinese side conducted surveillance and "vocal warnings to the US warship".
China claims almost the entire South China Sea and its islands, reefs and atolls on historic grounds. The area has some of the world's busiest shipping lanes and US officials say ensuring freedom of navigation is in American national interests, while not taking sides in the territorial disputes.
China seized the unpopulated Triton Island, an area of 0.46 sq. miles, from former South Vietnam in 1974. In May 2014, China parked a huge oil drilling platform off the Vietnamese coast in the area, prompting Vietnam to sent fishing boats and coastguard vessels to harass the rig and nearby Chinese vessels.
Skirmishes led to collisions and the capsizing of at least one Vietnamese boat.