Japan Coast Guard officials are monitoring 4 Chinese patrol ships that sailed into Japanese territorial waters near the Senkaku Islands in the East China Sea.
The officials say the ships entered the vicinity of Uotsuri Island around 10 AM on Sunday. They say the ships sailed in Japanese waters for about 90 minutes.
As of 11:30 AM, they were about 25 kilometers west-south-west of Uotsuri, in an area called the "contiguous zone" just outside Japanese territorial waters. The officials are warning the ships not to re-enter Japanese waters.
This is the first time this year that Chinese patrol vessels have entered Japanese waters off the Senkakus. The last time they were spotted in the area was on December 30.
Japan controls the Senkaku Islands. The Japanese government maintains they are an inherent part of Japan's territory. China and Taiwan claim them.