Photo/IllutrationA fishing boat that later collided with a Japanese patrol vessel floats off the northwestern coast of the Noto Peninsula, Ishikawa prefecture, on Oct. 7. (Fisheries Agency via AP)

Prime Minister Shinzo Abe says Tokyo has lodged a protest with Pyongyang over a collision between a North Korean fishing boat that illegally entered Japan's exclusive economic zone and a Japanese patrol boat, pledging to step up measures against foreign poachers.

Japanese authorities on Monday rescued about 60 North Korean fishermen who were thrown to the sea after their ship collided with a Japanese Fisheries Agency inspection vessel and sank in Japan's exclusive economic zone off the country's northern coast.

Abe said Tuesday that Japanese authorities helped the fishermen onto another North Korean ship and let them go due to lack of evidence showing illegal fishing.

The area has been crowded with North Korean poachers. Experts say the increase is due to Pyongyang's campaign to boost fish harvests.