Three Chinese coastguard ships sailed through disputed waters off Japanese-controlled islands in the East China Sea on Sunday, the latest such incident in a bitter territorial row between the two Asian giants.
The 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 (00.00 GMT) and left the area around two hours later, the Japanese Coast Guard said. It was the fifth time this year that state-owned Chinese ships entered the zone and the first foray in six days.
China's State Oceanic Administration said on its website: "On February 23rd, China's coastguard ships 2151, 2113 and 2102 patrolled together into territorial waters surrounding China's Diaoyu islands."
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 (ADIZ) 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.
United States Secretary of State John Kerry has warned Beijing against unilateral moves to set up a similar air defence zone over the South China Sea, where the Philippines in particular has voiced worries about China's maritime claims.
Earlier this month, the top diplomat said the US would defend Japan against any attack, including over the disputed islands in the East China Sea.