These islands, called Senkaku in Japan and Diaoyu in China, are at the heart of a tense dispute between Tokyo and Beijing.

Tensions heightened on Thursday when a Chinese surveillance plane made a brief flight over the islets.

The Japanese government protested the move and responded with a dispatch of Japanese F-15 fighter jets to patrol the area.

China's foreign ministry on Friday defended the flight, saying Japanese aircraft and ships had repeatedly entered waters around the islands since September.

But Japanese Chief Cabinet Secretary Osamu Fujimura said that while Japan would work with China to deal with the situation in a peaceful manner, it would respond to any provocations to Japanese sovereignty.

Sino-Japanese relations took a tumble in September after Japan bought the territory from a private Japanese owner.