Four Chinese coast guard ships entered Japanese territorial waters around the Senkaku Islands in the East China Sea on Sunday, the Japan Coast Guard said.
The latest intrusion, which a coast guard vessel confirmed at around 11:30 a.m., was the first since Dec. 8. The Chinese ships were told to leave.
The ships entered from northwest of Uotsuri, one of the islets in the disputed chain, which has been administered by Japan for decades but has recently been claimed by China and Taiwan, the 11th Regional Coast Guard Headquarters in Naha, Okinawa Prefecture, said.
It was the 73rd day in which Chinese vessels have entered Japanese waters since Japan's effectively nationalized the uninhabited chain in September 2012.