NHK has learned that in late June a North Korean ship armed with a man-portable surface-to-air missile was sighted in Japanese fishing grounds in the Sea of Japan.
Sources told NHK that the Japan Coast Guard confirmed the presence of the North Korean official ship in the Yamatotai area off Noto Peninsula in Ishikawa Prefecture.
The sources say the missile was the same type as the SA-16, which was developed by the former Soviet Union. It reportedly has a range of 4.5 kilometers.
They say it was the first time that a North Korean ship armed with a missile has been confirmed in the Yamatotai area.
In 2001, a North Korean spy ship armed with the missile, sank after exchanging gunfire with a Japan Coast Guard patrol ship off Amami-Oshima Island in the East China Sea.
The Yamatotai area is located in Japan's exclusive economic zone and is one of the nation's major fishing grounds.
Japanese fishing boats have long operated in the area, catching squid and other marine products. But illegal fishing by foreign vessels, including some from North Korea and China, has become a problem in recent years.
The Japan Coast Guard has raised its alert level to ensure the safety of Japanese fishing boats operating in the area. It constantly deploys patrol vessels to deal with suspicious ships and analyzes North Korea's latest intentions.