Two China Coast Guard vessels that had entered and left Japan's territorial waters near the Senkaku Islands earlier Sunday re-entered the waters in the afternoon, the Japan Coast Guard said.
The vessels, which re-entered around 1:40 p.m., had previously intruded into the waters near the group of uninhabited islets that China claims in the East China Sea earlier that morning for several hours.
It was the ninth intrusion this year and the latest since a new law entered into force in China earlier this month that explicitly allows its coast guard to use weapons against foreign ships that Beijing sees as illegally entering its waters. Japan has lodged protests over the repeated intrusions.
The Chinese vessels tried to approach a Japanese fishing boat in the area carrying three passengers, the Japan Coast Guard said.
A Japanese patrol vessel deployed near the fishing boat to ensure its safety warned the Chinese ships to leave Japanese territory, it said.
Two other Chinese vessels have also been spotted cruising in the so-called contiguous zone just outside Japan's territorial waters. One of them appears to be armed with a cannon, the coast guard said.