Japan also summoned China's ambassador in Tokyo on Tuesday to lodge a protest after eight Chinese coast guard vessels entered waters near the islands, called Senkaku in Japan and Diaoyu in China.
The vessels' activities appeared to be part of a recent escalation of Chinese military and maritime activity ahead of the anniversary of the Japanese government's purchase of the islands, about 2,000 kilometers (1,240 miles) southwest of Tokyo, from their Japanese owner.
Defense Minister Itsunori Onodera vowed to increase caution and surveillance in the area as the anniversary is marked Wednesday.
Japan's purchase of the three main islands in the group one year ago escalated tensions between the countries, triggering violent anti-Japan protests in China and harming diplomatic and business ties.
On Monday, Japan's Defense Ministry scrambled jets after an unmanned aircraft believed to be Chinese flew near the islands. There were no airspace violations.
Japan' coast guard said there have been more than 200 intrusions by foreign vessels into Japanese-claimed waters near the islands in the past year.