One of the ships was equipped with a man-portable surface-to-air missile system, similar to the SA-16, which was developed by the former Soviet Union with a 4.5-kilometer range.
A similar missile system was mounted on a North Korean reconnaissance vessel that sank in 2001 near Amami Oshima Island during a shootout with a Japanese patrol ship at sea. A North Korean ship with MANPADS was seen for the first time in the area of the Yamato Gully in the Sea of Japan.
The Japan Coast Guard has stepped up measures to ensure the safety of the country's fishing vessels.
In recent years, North Korean and Chinese fishing schooners have frequently appeared in the exclusive economic zone of Japan near Yamatotai in the Sea of Japan. However, in June this year, despite the squid-fishing season, North Korean schooners did not enter the area; instead, the Japanese Coast Guard began to sight North Korean patrol ships in the area, the NHK broadcaster reported.