Four bodies, suspected of being from North Korea, were found Monday on the northern coast of Japan's main island, local authorities said.

Three of the bodies, believed to be men, were discovered in Yamagata Prefecture, on the Sea of Japan coast. Two were wearing clothing with badges depicting the late North Korean founder Kim Il Sung, Japan Coast Guard officials said, but all three bodies were badly damaged, likely from their time in the water.

One was found floating in waters near a fishing port after the coast guard received a report from a fishing boat, while police were informed that two other bodies had been discovered on a beach some 500 meters away.

According to investigative sources, police are looking into potential links to a capsized wooden boat that was found Saturday on the adjacent Akita Prefecture's shore. In Akita, a body reduced to a skeleton and broken pieces of wood which appeared to be parts of a damaged boat were also discovered Monday.

There have been a string of cases in which unidentified wooden boats that appeared to have come from North Korea have washed ashore on the Japanese coast along the Sea of Japan.

Eight North Korean men were taken into protective custody by police after a wooden boat was found on the shore of Akita on Nov. 23.

On Nov. 26, another wooden boat apparently from North Korea was found on a different part of the prefecture's shore and eight bodies were later discovered in the boat.