The visit by Serdyukov risks again upsetting Tokyo after President Dmitry Medvedev last year sparked a major diplomatic crisis with Japan when he became the first Russian leader to visit one of the disputed islands.

Serdyukov left the Far Eastern Russian city of Khabarovsk for the "18th artillery division based on the Kuril islands of Iturup, Kunashir and Shikotan," ITAR-TASS quoted the defence ministry as saying.

"During today's visit, the minister will inspect issues of battle readiness, the supplying of the forces and also the social situation of the servicemen and their families," it added.

No further details were given over the visit.

The Kuril Islands, which lie north of Japan's Hokkaido island, have been controlled by Moscow since they were seized by Soviet troops in 1945 but their status is a major problem in Moscow-Tokyo relations.

The dispute surrounds the southernmost four islands -- known in Russian as Iturup, Shikotan, Habomai and Kunashir, which are collectively known in Japan as the Northern Territories.

Japan does not contest Russia's sovereignty over the northernmost islands but has repeatedly demanded the return of the four southernmost islands and it is the latter that Serdyukov was visiting Friday.

Russian and Japanese officials have repeatedly expressed frustration that the dispute has prevented relations reaching their full potential but summit meetings over the last years have failed to make any progress in the dispute.

The row has also prevented Russia and Japan from signing a peace treaty to formally end World War II.