Three Chinese coastguard ships sailed through disputed waters off Tokyo-controlled islands in the East China Sea Saturday, the Japanese coastguard said, the latest such incident in a bitter territorial row between the Asian giants.
The state-owned Chinese vessels entered the 12-nautical-mile territorial waters off one of the Senkakus, which China claims and calls the Diaoyus, at around 9:00am (0000 GMT) and left about two hours later, it said.
Chinese vessels and aircraft have regularly approached the East China Sea archipelago -- thought to harbour vast natural resources -- after Japan nationalised some of the islands in September 2012, setting off the latest spate of incidents in a long-running territorial dispute.
Fears of conflict rose in November when China imposed an air defence identification zone over the East China Sea and said it required notification from planes crossing the area.
Washington was angered by the move, saying it could lead to confusion in the skies.
US Defense Secretary Chuck Hagel held talks with his Japanese counterpart Itsunori Onodera last week and warned China against unilateral action to resolve a territorial dispute with Japan or other Asian countries.
China's defence minister, defending his country's claim, said on Tuesday that Beijing would not act first to "stir up troubles" over island disputes with its neighbours.