Ghost ships believed to be from North Korea appear off Japan

Several wooden boats, some carrying skeletons, have mysteriously appeared off Japan in recent weeks. Authorities are still investigating where the so-called ghost ships came from, but experts say all signs point to North Korea.

The Japanese coast guard on Thursday recovered one decrepit vessel drifting off the western coast of Matsumae on the northern island of Hokkaido. Ten men found aboard the wooden ship identified themselves as North Koreans and said they were taking refuge at an island nearby because of rough weather.

PHOTO: A wooden boat, top, is seen near a patrol ship of Japan Coast Guard off Matsumae, Hokkaido, Japan, Nov. 29, 2017. (Iori Sagisawa/Kyodo News via AP) More

PHOTO: A wooden boat is seen off Matsumae town, Hokkaido northern Japan, Nov. 29, 2017. (Iori Sagisawa/Kyodo News via AP) More

On Monday, the partly decomposed bodies of eight men were discovered on a rickety wooden boat on the coast of Japan's Akita prefecture, which faces North Korea across the Sea of Japan. Members of the coast guard first spotted the unidentified ship Saturday, but rough seas prevented them from approaching it at the time.

"The coast guard and police have to cooperate to step up sea patrols around Japan," Japan's Chief Cabinet Secretary Yoshihide Suga told reporters at a press briefing Tuesday night when asked about the grim find. "The government intends to improve this to ensure we can guard against suspicious boats or people arriving in Japan."

Suga declined to speculate about the vessel's origin, saying the investigation is ongoing. However, a coast guard official in Akita, who spoke to The Associated Press on condition of anonymity, said one of the bodies was holding a 1,000 won North Korean note.

The coast guard and Akita prefecture officials did not immediately respond to ABC News' requests for comment Saturday.

PHOTO: A wooden boat found by Japan Coast Guard after it drifted ashore with eight partially skeletal bodies is pictured in Oga, Akita Prefecture, Japan, Nov. 27, 2017. (Kyodo/via Reuters) More

Last week, Akita prefecture police officers rescued eight unknown men from another wooden ship seen drifting near the city of Yurihonjo's marina on the night of Nov. 23, according to Suga.

The men, who appeared to be healthy, told police they are from North Korea and their ship broke down while they were fishing, causing them to drift all the way to Japan's west coast. Authorities are investigating their claims, Suga said.

PHOTO: A wooden boat is moored at a nearby marina, in Yurihonjo, Akita prefecture, northern Japan, Nov. 24, 2017. (Kyodo News via AP) More

PHOTO: The wreckage of a boat is pictured along a sea wall in the city of Yurihonjo, Akita prefecture, Japan, Nov. 24, 2017. (AFP/Getty Images) More

On Nov. 15, the coast guard rescued three men from a capsized vessel off Japan's Noto Peninsula in Ishikawa prefecture. The men told authorities they are North Korean, and they asked to return home, Suga said. The incident is being investigated.

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