Japan has urged Russian Prime Minister Dmitry Medvedev not to visit Japan-claimed islands off Hokkaido, Foreign Minister Fumio Kishida said, calling the planned trip to the isles at the center of a long-standing bilateral dispute "unacceptable."

The planned visit, seen by experts as underlining Moscow's intention to reassert its control of the four islands, comes at a time Tokyo and Moscow are making preparations for President Vladimir Putin's visit to Japan later this year, Kyodo News Agency reported on Friday.

Kishida said at a press conference that the visit, if it takes place, would "go against Japan's position on the territories and hurt the feelings of the Japanese people".