Four Chinese patrol ships have entered Japan's territorial waters near the Senkaku Islands in the East China Sea.
The Japan Coast Guard reports the ships entered the waters off Uotsuri Island at around 10:10am on Monday.
The Coast Guard warned the vessels to leave immediately.
The Chinese ships cruised in the waters around the island for about one-and-a-half hours, and left the Japanese territorial water at around noon.
Chinese patrol ships last entered waters off the Senkakus on August 29.
Japan controls the Senkaku Islands. The Japanese government maintains that the islands are an inherent part of Japan's territory. China and Taiwan claim them.