Awwal 01, 1432, Feb 04, 2011, SPA -- Russia's defence chief visited military installations on islands at the centre of a dispute with Japan on Friday, in a move likely to anger Tokyo ahead of the Japanese foreign minister's visit to Moscow next week, according to Reuters. Defence Minister Anatoly Serdyukov visited Russian garrisons on the islands of Kunashir and Iturup and made a helicopter trip over Shikotan, a ministry spokesman said. It was the latest in a string of visits by Russian officials after President Dmitry Medvedev made the first trip by a Russian leader to the islands, which Russia calls the Southern Kuriles and Japan calls the Northern Territories, in November. Soviet troops occupied the four islands off Japan's Hokkaido in 1945. Soviet leader Josef Stalin felt he had U.S. and British approval to take them in return for entering World War Two against Japan. They have remained in Moscow's hands since and have been a persistent irritant in its ties with Tokyo. Moscow has pointedly asserted its sovereignty over the small islands off Russia's Pacific Coast with the visits by Medvedev and two senior government officials in recent months. Japanese Prime Minister Naoto Kan called Medvedev's visit "unacceptable". Russia has urged Japan to focus on economic ties with Russia rather than on the islands. Japanese Foreign Minister Seiji Maehara is scheduled to visit Moscow at the end of next week. Shortly after his trip to the islands, Medvedev invited Kan to visit Russia this year, and Kan tentatively accepted the invitation.