China has said it is closing off part of the South China Sea for military exercises this week.
The move comes days after an international tribunal ruled against Beijing's claim to ownership of virtually the entire strategic waterway.
Hainan's maritime administration said an area south-east of the island province would be closed from Monday to Thursday, but gave no details about the nature of the exercises. The navy and Defence Ministry had no immediate comment.
The announcement came in the middle of a three-day visit to China by the US Navy's top admiral to discuss the South China Sea dispute and ways to increase interactions between the two militaries.
Chief of Naval Operations Admiral John Richardson is meeting China's navy commander, Admiral Wu Shengli, during his trip to Beijing and the port city of Qingdao which began on Sunday. He is also scheduled to visit the navy's submarine academy, tour China's first aircraft carrier and discuss ongoing Rim of the Pacific military drills.
China rejected last Tuesday's ruling by the Hague-based Permanent Court of Arbitration in a case initiated by the Philippines, and refused to take part in the arbitration. It has responded by asserting that islands in the South China Sea are "China's inherent territory", and said it could declare an air defence identification zone over the waters if it felt threatened.
In a further show of defiance, Beijing followed the ruling by landing two civilian aircraft on new airstrips on the disputed Mischief and Subi reefs and dispatched its coast guard to block a Philippines fishing boat from reaching a contested shoal.
Dennis Blair, a former commander of US forces in the Pacific, told a congressional hearing on Wednesday that America should be willing to use military force to oppose Chinese aggression at a disputed reef off the coast of the Philippines. Mr Blair said the objective of such an action was not to pick a fight with China at the disputed Scarborough Shoal, but to set a limit on its military coercion.
Philippines President Rodrigo Duterte, who said before the ruling that he wanted to start talks with China on the issue, has not commented on the tribunal's decision, but described the territorial disputes as a complicated issue that may affect the country's economy as well as ties with treaty ally the United States.
Mr Duterte has been more reconciliatory with China compared with his predecessor, Benigno Aquino III, who filed the arbitration complaint against Beijing.
The tribunal ruled that China violated international maritime law by building up artificial islands in the South China Sea that destroyed coral reefs, and by disrupting fishing and oil exploration.
Six governments claim territory in the South China Sea, although the area where the Chinese naval exercises are being held is not considered a particular hotspot. China's navy and coast guard operate extensively throughout the South China Sea and regularly stage live firing exercises in the area.
China's island development has inflamed regional tensions, with many fearing that Beijing will use the construction of new islands complete with airfields and military facilities to extend its military reach and perhaps try to restrict navigation.
Several times in the past year, US warships have deliberately sailed close to one of those islands to exercise freedom of navigation and challenge the claims. In response, China has deployed fighter jets and ships to track and warn off the American ships, and accused the US of threatening its national security.