VLADIVOSTOK/MOSCOW (Kyodo) -- Russia on Tuesday began a military exercise on two of the four disputed islands to Japan's north, the Interfax news agency reported.
The drill on Etorofu and Kunashiri islands involves about 500 troops from machine gun and artillery units practicing the prevention of enemy landings, it said.
The Japanese government immediately lodged a protest over the exercise through diplomatic channels, the Japanese Embassy in Moscow said.
Japanese Prime Minister Shinzo Abe is seeking to resolve a decades-old territorial dispute with Moscow over four islands off Hokkaido in northern Japan and sign a broad agreement on a postwar peace treaty in June when Russian President Vladimir Putin is due to visit Japan for the Group of 20 summit.
Abe and Russian President Vladimir Putin agreed in November to accelerate peace treaty talks based on a 1956 joint declaration which mentions the transfer from Moscow to Tokyo of the smaller two of the four islands -- Shikotan and the Habomai islet group -- once a peace pact is concluded.
But their talks have made little progress, as deep divisions remain over the territorial dispute, with Russia stressing that Japan must recognize the acquisition by Moscow of the four islands as the outcome of World War II, while Tokyo maintains the islands were illegally seized by the Soviet Union following Japan's 1945 surrender.
The feud over the islands, called the Northern Territories in Japan and the Southern Kurils in Russia, has prevented the conclusion of a peace treaty to formally end World War II