Japan's prime minister has vowed to defend disputed remote islands from escalating threat from China.

Prime Minister Shinzo Abe called on Japan's Self-Defense Forces on southern Japan on Saturday, saying the disputed islands in the East China Sea are under increasing threat.

Abe said he will defend them "at all costs."

The uninhabited islands are controlled by Japan but also claimed by China. Japan's nationalisation of the islands in September triggered violent protests across China, hurting Japanese companies there and the economy.

China has sent surveillance ships regularly to waters near the islands, and aircraft from the two sides have trailed each other, raising the risk of missteps that could trigger a clash.

Japan has recently launched diplomatic efforts to ease tensions, with China-friendly officials visiting Beijing for talks.