The entry of the vessels appeared to renew tensions between the two countries after a brief diplomatic lull over the disputed islands in the East China Sea, which are also claimed by China. Bilateral relations have worsened since early September when Japan nationalized the uninhabited islands, which are called Diaoyu in China.
The Japanese coast guard said the three vessels moved into its waters just after noon Wednesday, ignoring its warnings. Earlier, the three vessels and fourth Chinese ship were seen in the contiguous zone just outside Japanese waters, Kyodo News said.
In earlier intrusions, the report said six Chinese surveillance vessels traveled in the contiguous zone Monday with four of them later entering Japan's territorial waters Tuesday.
The coast guard's regional headquarters in Naha in Okinawa said the Chinese vessels have not responded to their demands that they leave Japanese waters but there had been no response.
There was no immediate report from the official Chinese media on Wednesday's developments but the official Xinhua news agency said four Chinese maritime surveillance ships conducted a patrol off the Diaoyu Islands "keeping close watch on the illegal entrance of the Japanese right-wingers in the areas, according to the State Oceanic Administration."