Five Japanese ships illegally broke into the territorial waters of Diaoyu Island on Monday, according to a spokesperson of the China Coast Guard.

The coast guard ships took the necessary measures to warn them away, spokesperson Gan Yu said.

Diaoyu Island and its affiliated islets are inherent territory of China, Gan said.

Japan has no right to point fingers at China Coast Guard for carrying out legal and normal missions in areas under China's jurisdiction, the spokesperson said.

"We urge the Japanese side to stop illegal activities in this area, and make sure this won't happen again," Gan said.