Some Japanese officials' comment on Russian leader's planning visit to the Southern Kurils islands was inappropriate, the Foreign Ministry said Monday.

"Southern Kurils islands have been Russia's inseparable part. The comments from abroad over Russian leader's planning trip in their own territory are inappropriate, at least," Foreign Ministry said in a statement published on its website.

Russian news website Sakh.com reported Sunday Prime Minister Dmitry Medvedev was going to visit the Etorofu isle in early July. Japanese Chief Cabinet Secretary Osamu Fujimura told a news conference Monday that the top Russian official's upcoming visit was contrary to Japan's stance and "unpleasant."

Moscow and Tokyo have been at odds over the four isles called by Japanese as the Northern Territories since the end of the World War Two.

The disputed isles, including Etorofu, Kunashiri, Shikotan and the Habomai islet group, were seized by the Soviet Union following Japan's surrender in World War II.

Relations between Russia and Japan have been clouded due to the heated territorial dispute which erupted once again after Russian then-president Medvedev visited Kunashiri in November 2010.