The People's Liberation Army's Southern Theater Command conducted a routine patrol in the South China Sea on Wednesday, a spokesperson said.

Tian Junli, spokesperson for the command, announced the operation in a statement Wednesday evening, criticizing the Philippines for working with outside countries on "so-called joint patrols," which he said created instability in the region.

The Philippines' actions were an attempt to justify its "illegal claims" in the South China Sea and undermine China's legitimate maritime rights and interests, Tian said.

"The theater command forces remain on high alert, resolutely defending national territorial sovereignty and maritime rights and interests. Any military activities that disrupt the South China Sea are fully under control," he said.