A visit this month by Japanese to the Russian-held islands off Hokkaido under a visa-free exchange program has been canceled due to Russia’s request for the submission of certain travel documents, sources said.

The documents, which Russia says have become necessary due to legal changes, include applications by foreigners for the registration of visits when former Japanese residents of the islands stay there for more than seven hours a day, as well as embarkation cards.

It is extremely rare for the exchange program with Russian islanders to be suspended due to reasons other than bad weather. The move is viewed as a sign of Russian displeasure with Japan, which has followed the United States and European nations in imposing sanctions on Moscow after its annexation of Crimea last year.

An official of the Russian Foreign Ministry said the trip has been temporarily suspended because of practical reasons and has not been canceled, citing ongoing “internal arrangements among related organizations.”

The Japanese Foreign Ministry’s Russian Division declined Monday to explain the details, with an official only saying that “discussions have taken place on various points.”

According to the sources, Russian officials said in March during a meeting with Japanese officials in Sapporo to the discuss visa-free exchanges that the registration of visits is now required because of legal changes in Russia last year.

They said that if the rules are not followed, hefty fines will be imposed on Russian organizations that accept Japanese visitors.

Japanese vessels used for the exchange program should also follow the procedures for foreign ships, they said.

Japanese officials said they will not agree to any kind of embarkation formalities because accepting the procedure would mean Japan recognizes Russian jurisdiction over the disputed islands.

But they also proposed making the former residents’ visits to the islands shorter.

Russian officials have passed the Japanese officials’ proposal on to their superiors, but told Japan last Wednesday of the suspension of the exchange program, shortly before the planned departure of the former Japanese residents of the islands.

The visa-free visit program started in 1992 as part of efforts to deepen mutual understanding.

The four islands off Hokkaido — Etorofu, Kunashiri, Shikotan and the Habomai islet group — were seized by the Soviet Union following Japan’s surrender in World War II.

The row over ownership of the islands has prevented the two countries from signing a postwar peace treaty.

In Moscow on Monday, Japan and Russia held vice minister-level talks on economic affairs.

Tokyo is hoping stronger economic ties with Moscow will pave the way for President Vladimir Putin to visit Japan this year and help move forward the long-stalled negotiations for the return of the islands.

During the talks, the participants also made arrangements for Foreign Minister Fumio Kishida to visit Russia, which Moscow expects to take place before Putin travels to Japan.