TOKYO, Jan. 7 (UPI) -- Four Chinese ships entered Japanese territorial waters near the disputed Senkaku Islands in the East China Sea Monday, the Japanese Coast Guard said.
The ships were observed sailing around the island chain for the first time since a similar incident Dec. 31, Japan's Kyodo News reported.
The Chinese State Oceanic Administration said the vessels are marine surveillance ships meant to patrol the waters around the islands, which the Chinese call Diaoyu, Xinhua reported.
Officials at the Regional Coast Guard Headquarters in Naha, Okinawa, said the Japanese Coast Guard asked the four ships to leave the area.
Tensions between Japan and China over competing claims to the islands have worsened since September when the Japanese government announced the nationalization of the islands.