Japanese authorities are looking into a spate of incidents in which small boats, apparently from North Korea, have washed up on beaches the length of northern Japan.
In the last two months, police and the Japan coastguard have been called out to deal with 11 wooden fishing boats, mostly in a poor state of repair, either drifting off the coast or on beaches facing North Korea across the Sea of Japan, or East Sea.
The bodies of 25 people were found aboard the vessels, a coastguard official confirmed.
"We are carrying out an investigation into these vessels and where they come from, although reports that Hangul characters were on the boats are correct," said coastguard spokesman Yoshiaki Hiroto, referring to the Korean alphabet.
"Fishing equipment was also found aboard the boats."
In one of the most recent discoveries, a wooden boat was found adrift off Wajima, in Ishikawa Prefecture, last Friday. Hangul characters, written in red on the hull of the ship, read 'Korean People's Army No. 325'.
The abandoned ship, which was 12 metres long, contained nets and fishing equipment.
Japanese authorities are working on the assumption that the boats are fishing vessels that strayed too far from the North Korean coast and either ran out of fuel or suffered some sort of engine malfunction before being taken by the currents to Japan.
Not anticipating an extended period at sea, the crews probably perished from exposure to the elements or from a lack of food and water.
An alternative suggestion would be that at least some of the boats were attempting to get defectors out of North Korea.
In September 2011, nine people were rescued off the coast of northern Japan after a five-day voyage in a small boat. The three men, three women and three young children told the coastguard they were from the same family and had been attempting to travel to South Korea to seek asylum.
The Japanese government permitted the defectors to continue on to South Korea.
Analysts said it was unlikely the vessels were being used to infiltrate North Korean agents into Japan or to smuggle drugs, although the police and coastguard do keep a careful watch on the movements of suspicious boats in the area, particularly after a violent clash that took place between the coastguard and an armed North Korean ship off Amami-Oshima in December 2001.
Discovered inside Japan's exclusive economic zone, the North Korean ship was ordered to stop for an inspection. A fierce fire-fight and chase broke out, lasting six hours, at the end of which the North Korean vessel blew itself up and the crew of 15 died.
"If the North learned anything from that incident it would have been that it's just easier for them to infiltrate someone into Japan using a fake passport and putting them aboard a flight or a ferry ship to Japan," said Robert Dujarric, director of the Institute of Contemporary Asian Studies at the Japan campus of Temple University.
"We know that the regime in North Korea is pushing its farmers and fishermen to produce greater amounts of food and, to my mind, the most likely explanation is that these were simply fishermen who were trying to fulfil large quotas and simply ran out of fuel too far out at sea to get home."
