Washington's attempts to interfere in a dispute between Russia and Japan over the Kuril Islands are "unacceptable," the Russian Foreign Ministry's official spokesman said on Thursday.

The Russian Foreign Ministry on Monday summoned U.S. ambassador to Moscow John Beyrle to express concern over the U.S. statements in support of Japan's territorial claims on the islands amid Tokyo's recent tough rhetoric.

"We consider it totally unacceptable to attempt to meddle in this matter, which is bilateral," Alexander Lukashevich said, adding such action did not contribute to finding a "constructive solution" to such a sensitive problem.

Japan's continued claim over four South Kuril Islands has prevented Moscow and Tokyo from signing a formal peace treaty to end World War II hostilities. Iturup, Kunashir, Shikotan and Habomai, known in Japan as the Northern Territories, lie at the end of a chain stretching from Russia's Kamchatka Peninsula to the Japanese island of Hokkaido.

Tensions escalated in November last year when Russian President Dmitry Medvedev visited one of the disputed islands, an act Japanese Prime Minister Naoto Kan criticized as "inexcusable rudeness."

MOSCOW, February 24 (RIA Novosti)