China repelled a U.S. destroyer on Thursday after it trespassed in territorial waters surrounding the Xisha Islands in the South China Sea without Chinese government approval, and expressed firm opposition to the U.S.'s illegal action, China's Ministry of National Defense said in a statement. 

The Xisha Islands are Chinese territory, and the U.S.'s action is a grave provocation that infringes on China's sovereignty and endangers peace and stability in the South China Sea, according to the statement. 

China urges the U.S. to clearly understand the situation and stop provocations. The Chinese military will take all necessary measures to respond to all threats and provocations, resolutely safeguard national sovereignty and security, and firmly safeguard regional peace and stability, the statement said.