Japan has urged Russian Prime Minister Dmitry Medvedev not to visit disputed islands off Hokkaido, Foreign Minister Fumio Kishida said Friday, 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 when Tokyo and Moscow are making preparations for President Vladimir Putin's visit to Japan later this year.

Kishida said at a news 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."