North Korea’s coastguards have detained a Russian yacht in the Sea of Japan, Russia’s foreign ministry says.

According to Russian reports, the yacht Elfin with five crew on board was intercepted as it was returning to Russia after participating in a competition in South Korea.

Russian diplomats have demanded the crew’s immediate release and an explanation.

However, Russia is one of the few countries that have relatively friendly ties with North Korea.

The Elfin was on its way from South Korea’s port city of Busan to Vladivostok in Russia’s far east when it was detained 80 miles off the coast on May 13, the foreign ministry said.

The yacht was taken into the North Korean port of Kimchaek and the crew were not in any danger, the ministry added.

The Russian consul-general was waiting for permission to visit them, it said.

Russia shares a short land border with North Korea.