Russian Foreign Minister Sergei Lavrov called on the Japanese authorities on Tuesday to prosecute Japanese radicals for desecrating a Russian flag during protests over a territorial dispute between the two countries.

Japanese ultra-right campaigners dragged the Russian flag along the ground outside the Russian Embassy in Tokyo on Monday amid the heating up of a diplomatic row between Russia and Japan over four islands off Russia's Far Eastern coast, called the Northern Territories in Japan and the Kuril Islands in Russia.

"Not only did we protest, but we also asked the Japanese authorities to launch a criminal case over the desecration of the Russian flag," Lavrov said. "We were told that in Japanese law there is an article that forbids the mockery of foreign state symbols."

On Monday, during Japan's Northern Territories Day, Japanese Prime Minister Naoto Kan called Russian President Dmitry Medvedev's recent visit to one of the islands an "inexcusable rudeness," sparking an angry reaction from Moscow.

The sparsely populated islands in the Kuril chain between Japan's northern island of Hokkaido and Russia's far eastern Kamchatka Peninsula were annexed by the Soviet Union at the end of World War II.

Lavrov said the incident will not affect a forthcoming visit of Japanese Foreign Minister Seiji Maehara to Moscow on February 11.

MOSCOW, February 8 (RIA Novosti)