A top government spokesperson says Japan will urge Russia to resume an exchange program that enables Japanese citizens to visit their ancestors' graves on Russian-held islands.

Russia controls the four islands. Japan claims them. The Japanese government maintains that the islands are an inherent part of Japan's territory. It says the islands were illegally occupied after World War Two.

The annual grave visits and other exchange programs relating to the islands have been suspended since Russia began its invasion of Ukraine last year. This year, former residents and their families are due to set sail on Monday to hold the first of a series of ceremonies at sea to pay tribute to their ancestors.

Chief Cabinet Secretary Matsuno Hirokazu told reporters on Friday that the government is contacting Russia through diplomatic channels, but has received no positive response so far on resuming the grave visits.

Matsuno said the government remains determined to meet the wishes of the aging former islanders.

He said resuming the exchange programs is one of the top priority issues in Japan-Russia relations. He added that Japan will place particular emphasis on seeking the restart of the grave visits.