Three Chinese coast guard ships intruded into territorial waters around the disputed Senkaku Islands in the East China Sea for about two hours Tuesday, the Japan Coast Guard said.
Chinese coast guard vessels last entered Japanese territorial waters on Dec. 23. Chinese government ships have been spotted intruding there on 32 days since the beginning of this year.
A Japan Coast Guard patrol ship issued a warning urging the ships, identified as the Haijing 2102, 2166 and 2401, to leave the waters. One of them responded that the islands are "inherent territory of China," according to the 11th Regional Coast Guard Headquarters in Naha, Okinawa Prefecture.
China contests Japan's sovereignty over the Japanese-administered, uninhabited islands, which it calls Diaoyu. Its ships have repeatedly entered the waters around them in recent years, raising tensions between the two countries. Taiwan also lays claim to the islands.