The Chinese People's Liberation Army (PLA) expelled American guided-missile destroyer USS Curtis Wilbur after it trespassed into China's territorial waters near Xisha Islands in the South China Sea, said Tian Junli, a spokesperson for the PLA Southern Theater Command, in a statement published on Thursday.

Tian called the U.S. a "true troublemaker" in the South China Sea, adding that it sent its warship into China's territorial waters without permission.

On Thursday afternoon, Chinese Foreign Ministry spokesperson Zhao Lijian also expressed China's firm opposition to the U.S. trespass, stressing that the move is a gross infringement on China's sovereignty and national security.

It undermines the peace and stability in the South China Sea, Zhao said, urging the U.S. side to immediately stop such provocative actions.

He said China will continue taking resolute actions to defend its national sovereignty and security and maintain the peace and stability of the region.

Late Thursday, Tan Kefei, spokesperson for the Ministry of National Defense, also reiterated that Taiwan is an integrated part of China and that questions regarding Taiwan region are purely China's internal affairs which allow no interference.

Noting that Taiwan issue is the most important and most sensitive issue in China-U.S. relations, Tan warned the U.S. side to abide by the one-China principle and the three China-U.S. joint communiques, properly handle the situation and stop making trouble for bilateral relations.