Senior Japanese and Russian diplomats on Tuesday agreed to further promote negotiations over planned joint economic activities on four disputed islands off Hokkaido, Japanese officials said.

The vice ministerial talks in Tokyo over the Russian-held islands came ahead of Prime Minister Shinzo Abe's scheduled visit to Moscow in May. The Japanese officials, however, did not offer any details of concrete progress.

"We held detailed discussions ... on five possible activities, based on the principle that they will not undermine legal positions" of the two nations on the islands, Senior Deputy Minister for Foreign Affairs Takeo Mori told reporters after the meeting.