Japan's Coast Guard says four Chinese government vessels entered Japanese territorial waters off the Senkaku Islands early on Monday.
The vessels were reportedly approaching a Japanese fishing boat. Coast Guard personnel are trying to ensure the safety of the Japanese fishers, and they are warning the Chinese vessels to immediately leave the waters.
Japan controls the islands. The Japanese government maintains that the islands are an inherent part of Japan's territory. China and Taiwan claim them.
The Coast Guard says the four Chinese ships entered Japan's waters off Uotsuri Island and Minamikojima Island, two of the Senkaku Islands, one after another starting at around 2:40 a.m.
It says that, as of 3:30 a.m., three of the vessels were sailing 12 to 17 kilometers south of Uotsuri Island. It says the other was traveling about 15 kilometers south-southwest of Minamikojima Island.
This is the 28th occasion this year on which Chinese government ships have been confirmed to be navigating in Japan's territorial waters off the Senkaku Islands. The last intrusion was reported on Saturday.