NEW : Japanese Foreign Minister Sergey Lavrov denies the visit is worth a comment . Following Japan 's defeat in World War II in 1945 , the Soviet Union annexed the four southernmost islands , which previously belonged to Japan . Russian Prime Minister Sergey Lavrov visits Kunashir Island , near Japan 's island of Kunashir Island . Hokkaido calls the visit `` wrong '' The islands have been a source of dispute between the four countries since World War II .
NEW : Japanese Foreign Minister Sergey Lavrov denies the visit is worth a comment . Russian Prime Minister Sergey Lavrov visits Kunashir Island , near Japan 's island of Kunashir Island . Hokkaido calls the visit `` wrong '' The islands have been a source of dispute between the four countries since World War II .