The Chinese army acted immediately and dispatched warships to warn US warships that had entered the South China Sea on Sunday to leave, ‍China's Ministry of National Defense said.

The two warships, Higgins, a guided-missile destroyer and Antietam, a guided-missile cruiser, arbitrarily entered waters surrounding China's Xisha Islands, the ministry said. 

It said the Xisha Islands are an inherent part of China's territory.

China, the statement continued, resolutely opposes the US actions which go against China’s laws and relative international laws. 

The Chinese army is determined to strengthen naval and air combat readiness, improve defense levels, safeguard national sovereignty and security and safeguard regional peace and stability, the ministry said.

The Chinese Foreign Ministry also responded to the encroachment, saying China will continue to take all necessary measures to defend its national sovereignty and security.