Japan's Defense Ministry has restated its protest against a South Korean naval ship for directing fire-control radar at a Japanese patrol plane.
The incident Thursday involved a South Korean destroyer and a P-1 patrol aircraft of the Maritime Self-Defense Force. It took place over the Sea of Japan off the Noto Peninsula in Ishikawa Prefecture.
Japan first lodged a protest with South Korea on Friday.
South Korea dismissed the complaint, saying the destroyer used the radar during a search for a drifting North Korean ship.
It said there was no factual basis to the assertion it was tracing the MSDF aircraft.
In response, the Japanese defense ministry said Saturday that fire-control radar is used to acquire information about a target, including its precise orientation, before launching an attack.
The ministry said this type of radar is not suitable for searching a wide area.
It condemned the radar's use as a dangerous act that could have unexpected consequences.
The ministry said even if such radar is used to search for a ship, it poses a danger to other vessels and aircraft in the area. It added that international norms say such acts should be avoided.
The Japanese government called on Seoul to take preventive steps to avoid a repeat of such incidents.