China’s defence ministry said on Saturday that a PLA garrison on an island in a disputed area of the South China Sea had taken action to warn off and repel a US Navy destroyer that had entered its territorial waters. Defence ministry spokesperson Yang Yujun said in a statement that China strongly opposed the “provocative move” by the United States. The Pentagon had earlier said that the USS Curtis Wilbur had sailed within 12 nautical miles of Triton Island in the South China Sea on Saturday. A Pentagon spokesman Jeff Davies said the aim of the patrol was to challenge efforts to restrict freedom of navigation in the area. “This operation challenged attempts by the three claimants - [mainland] China, Taiwan and Vietnam - to restrict navigation rights and freedoms,” he said. Davis said no ships from China’s military were in the area when the US warship carried out its patrol in the Paracel islands on Saturday. However, Yang said the PLA garrison on the island had given warnings and taken action to expel the US warship. He did not give details of what kind of action was taken. READ MORE: Warships sent, US ambassador called in as China bolsters Navy presence in disputed Spratly islands, after US sail-by rattles Beijing’s sovereignty claims The island is known as Zhongjian Dao in Chinese. It has been controlled by the PLA since 1974 after a naval conflict with Vietnam. It is the first time the US Navy has challenged China’s territorial claims in the Paracel islands. A US warship sailed within 12 nautical miles of Mischief and Subi reefs in the Spatly Islands in another disputed area of the South China Sea in October last year. The patrol incensed China’s government, which described the action as a dangerous provocation. Pentagon spokesman Davis said the latest operation sought to challenge policies that require prior permission or notification of transit within territorial waters. “No claimants were notified prior to the transit, which is consistent with our normal process and international law,” he said. A spokeswoman for China’s foreign ministry, Hua Chunying, said the US warship had acted illegally in entering Chinese waters, state television reported. She urged the US to respect China’s laws and do more to help maintain regional peace and stability. China claims most of the South China Sea, through which more than US$5 trillion of world trade is shipped every year. Vietnam, Malaysia, Brunei, the Philippines and Taiwan have rival claims. China has been rapidly developing man-made islands in the region, including building runways, increasing tensions among its neighbours. READ MORE: China’s neighbours wary of taking sides in Sino-US South China Sea dispute Li Jie, a Beijing-based naval expert, said the US operation was a direct challenge to China’s claims of sovereignty in the disputed waters. “The US is trying to test the bottom line of China in the South China Sea issue,” Li said. He described it as an “unfriendly move” that might challenge relations between the two countries. Ni Lexiong, a Shanghai-based naval expert, said the US action was a show of force. “The US wants to show other Asian countries that it has the power to challenge Chinese claims in the Paracel Islands,” he said.