The vessels were seen in the area at around 10:00 a.m. local time (0100 GMT) to the north-west of the Kubadzima Island. The Japanese border guards told China to “immediately leave Japan’s territorial waters” but took no active steps.
Tensions over the group of uninhabited islands increased in September 2012 after Tokyo announced plans to buy them from private owners. After that move, mass anti-Japanese protests hit China.
Since then, Chinese vessels have been repeatedly seen near the disputed Senkaku Islands, also known as the Diaoyu Islands in China.
Japan’s coastal guards have asked to double their budget in 2015 to $447 million to buy new patrol vessels and aircraft and organize round-the-clock patrolling of the area.
Beijing maintains that Japan had annexed the islands by force and they should be given back to China under the terms of Tokyo’s surrender during World War II. Japan has refused to negotiate the issue.