Two China Coast Guard ships entered Japanese territorial waters off the Senkaku Islands in the city of Ishigaki, Okinawa Prefecture, on Sunday.
As the two Haijing ships tried to approach a Japanese fishing boat, Japan Coast Guard patrol vessels secured the safety of the boat and warned the Chinese ships to leave the waters.
Chinese official ships were spotted in the waters near the Senkakus for the fourth consecutive day.
According to the JCG's 11th regional headquarters in Naha, the two Chinese ships entered Japanese waters including from a point south of Uotsuri Island in the Senkaku chain around 3:15 p.m. They were both equipped with what appeared to be cannons.
The Japanese-administered islands in the East China Sea are also claimed by China, where they are called Diaoyu.