TOKYO >> Japanese authorities were preparing Thursday to inspect a decrepit boat with 10 men identifying themselves as North Koreans drifting in rough seas off the northern island of Hokkaido.

Coast guard officials said they were towing the wooden boat to a safer area for inspection. Officials spotted the boat off the western coast of Matsumae town Tuesday but rough seas prevented them from approaching it.

The coast guard said the men communicated in Korean via loud speakers and a message board saying they were from North Korea and taking refuge at a nearby island due to rough weather. It was not immediately known whether the boat was involved in illegal fishing inside Japan’s 200-nautical mile exclusive economic zone.

Japan has been stepping up patrols after a recent spike in the number of boats turning up on its coasts.

Dozens of boats and debris wash up on Japanese northern coasts every year. This year, 59 cases — compared to 66 last year and down from 80 five years ago — have been detected, nearly half of them in November alone, according to the coast guard.

Officials said they were linked to a reported campaign by the North to send fishermen farther out for more catches.

It’s unclear if people aboard those boats that drift near Japanese shores each year intend to defect or are simply unable to make their way back in unseaworthy wooden vessels. Officials say the boats are frequently pushed toward Japan during winter due to a seasonal wind.

In Akita on Monday, officials found 10 bodies inside a ragged wooden boat believed to be from North Korea after it washed up on the beach. Last week, a group of eight men who say they are from North Korea washed ashore and are being investigated. Authorities said they were not asylum seekers and had expressed wish to return home.