Four Chinese government vessels entered Friday in waters of islands administered by Japan but claimed by China, the Japanese coast guard said.
According to AFP , the marine surveillance ships went around 11.30 local time (04.30 GMT) 22 kilometers in area surrounding the Senkaku Islands in the East China Sea (called Diaoyu by Beijing), the Coast Guard said.
They have been spotted near the island Uotsuri, the main of this small archipelago that caused a serious deterioration in relations between Beijing and Tokyo over the past two months.
Tension rose in early September, after the Japanese government decided to purchase more of these islands from the Japanese private owner.
Immediately, Beijing decided to send six ships to the islands, while in China took place during one week antijaponeze demonstrations, sometimes violent, with the tacit approval of the authorities.