Image copyright AFP Image caption The bodies were discovered on badly damaged boats at Fukui port in western Japan

Japanese officials are investigating after up to 11 boats were found drifting off the country's coastline - some with decaying bodies on board.

Around 20 corpses were found on wooden boats between October and November, a coastguard spokesman said.

Many of the boats have been towed to Japanese ports, but the bodies are yet to be identified.

Korean writing is reported to have been found on the vessels, leading some to suggest they came from North Korea.

Coastguard personnel spotted a boat with three sets of remains inside on Tuesday and pulled it ashore at Fukui port, Tokyo Broadcasting System reported.

The bodies were badly decomposed and partially skeletonised, it added.

This is not the first incident - in 2012, the decomposed bodies of five males were discovered off Japan's west coast.

Experts suspect the vessels are North Korean fishing boats lost due to a lack of modern equipment, according to local media.