Japan's Chief Cabinet Secretary Yoshito Sengoku said Tuesday a visit by a senior Russian politician to disputed islands off Hokkaido claimed by both countries would be of no benefit to Russia's plans of developing its Far East region.

"Japan will tenaciously express its deep regret if a senior Russian politician visits the four disputed islands," said Sengoku at a press conference after Russia's First Deputy Prime Minister Igor Shuvalov visited two of the four disputed islands Monday.

"We have to send a strong sign that such a move despite Japan's protest would not benefit Russia's efforts to develop its Far East area," he said.

Russian President Dmitry Medvedev, who himself visited Kunashiri island in November, becoming the first leader from Russia or the former Soviet Union to visit any of the islands in person, instructed Shuvalov to visit Kunashiri and Etorofu islands and report back on their infrastructure, local Russian media reports said.

The disputed islands of Etorofu, Kunashiri, Shikotan and the Habomai rocks are believed by Japan to be a part of the Nemuro Subprefecture of Hokkaido Prefecture. Russia, however, ardently contests this and the territorial dispute over the four islands has prevented Japan and Russia from signing a postwar peace treaty.