China said on Saturday it had deployed its naval forces to stop a US warship sailing through disputed waters in the South China Sea.
A statement released by the Southern Theatre Command said the guided-missile cruiser USS Chancellorsville had entered the waters around the Paracel Islands on Wednesday without the approval of the Chinese government.
"The Southern Theatre Command organised navy and air forces to monitor the US vessel, and gave warning for it to leave," the statement said.
"The theatre command will continue close monitoring of the air and sea conditions to prevent the happening of events that poses a threat to national security".
The statement called on the US to properly manage its navy and air fleet to avoid miscalculations.
US Pacific Fleet spokesman Nathan Christensen said in a statement on Thursday that the US warship conducted the operation near the islands - known in China as the Xisha Islands - to challenge China's claim to the islands.
"USS Chancellorsville sailed near the Paracel Islands to challenge excessive maritime claims and preserve access to the waterways as governed by international law," he said.
China foreign ministry spokesman, Geng Shuang, said on Friday that the US ship had entered Chinese waters without permission and China had made its position known with its "stern representations".
The latest US operation in the South China Sea came weeks after US and Chinese warships nearly collided with each other in the disputed waters on September 30.
While it claims sovereignty over the South China Sea, China is in talks with surrounding countries over a code of conduct for the disputed maritime region.
It has long been opposed to US military aircraft and warships sailing near or flying over the disputed islands.
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Meanwhile, satellite images reviewed by a US think tank showed China has installed a new platform on a remote part of the Paracel Islands that could be used for military purposes.
The Asia Maritime Transparency Initiative of Washington's Centre for Strategic and International Studies said the images showed a "modest new structure" on Bombay Reef, topped by a radar dome and solar panels.
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The purpose of the structure was unclear, but the think tank said it could be for military use.
China has said some civilian facilities on the islands were intended for use by others in the region, but the government has given few details about how that may work in practice.
The islands China occupies in the South China Sea are off limits to foreigners, and access is under the effective control of the People's Liberation Army despite them technically being part of the province of Hainan.
Vietnam, Malaysia, the Philippines, Brunei and the self-ruled island of Taiwan also have competing claims in the South China Sea.
- South China Morning Post