“It is difficult to identify the bodies as they had begun to decompose,” he said, noting that rough seas had prevented officials from investigating the boat thoroughly.

“We spotted a tobacco box which carries some Korean letters, but we can’t confirm the boat came from North Korea,” he said.

However, coastguard officials believe it is the latest North Korean fishing vessel to wash up on the coast, following a record number of such cases last year.

Television footage showed the wreckage of the flat-bottomed vessel capsized on the beach.

According to TV Asahi, a badge depicting former North Korean leader Kim Jong-il was found in the wreckage.

The number of North Korean fishing vessels washing up on Japan’s coast hit a record 104 cases last year, following 66 in 2016, according to the Japanese coastguard.

Sometimes the crew members have already died at sea, a phenomenon local media refer to as “ghost ships”.

Experts say some North Korean fishermen are travelling further out to sea to satisfy government mandates for bigger catches.

But their old and poorly equipped vessels are prone to mechanical and other problems, including running out of fuel, and there are few ways for them to call for rescue.

A severe shortage of food and foreign currency – as international sanctions over Pyongyang’s nuclear and missile ambitions bite – are contributing to a wave of poorly equipped North Korean fishing boats washing up in Japanese waters, pundits say.

Japan and North Korea have a tense relationship, with Pyongyang routinely issuing verbal threats as well as firing missiles near or above Japan.

But the Japanese coastguard occasionally rescues North Korean fishermen in maritime accidents in regional waters.