TOKYO/SEOUL -- Japan's Ministry of Defense made public on its homepage Friday video footage of an incident last week in which a South Korean warship locked its fire-control radar on a Japanese patrol plane.

The 13-minute video (see it here) shows scenes from the afternoon of Dec. 20, off the coast of Japan's Noto Peninsula in the Sea of Japan.

A Japanese Maritime Self-Defense Force P-1 patrol plane is conducting surveillance close to a South Korean destroyer when a crew member detects fire-control radar projected on the aircraft. A lock-on with fire-control radar is considered a hostile act.

"The sound is so loud," a crew member says around six minutes into the video, referring to the radio field intensity.

The fire-control radar is directed at the Japanese plane multiple times. The Japanese side decides to contact the ship.

"Korean naval ship, Korean naval ship ... This is Japan navy," a Japanese crew member calls out over the radio. "We observed that your FC antenna is directed to us. What is the purpose of your act? Over."

The message is conveyed three times, but no response is received from the South Korean ship.

South Korea's Defense Ministry expressed deep concern and regret Friday over the disclosure of the video and reiterated its stance that fire-control radar was not used.

Criticizing the video as "one-sided," the South Korean ministry said it "cannot be regarded as objective evidence."

Yoji Koda, a former vice admiral of Japan's Maritime Self-Defense Force, commented on the lack of communication during the incident.

"When the plane asks what the intent of the radar projection is, it is standard procedure for the ship to respond," he said.

Koda noted that no adverse weather appeared in the video and that conditions for communication seemed normal.

"If the South Korean side intentionally did not respond, it will be a violation of international law," he said.

Park Hwee-rhak, a political scientist at South Korea's Kookmin University, said it was disappointing that the two U.S. allies were unable to resolve misunderstandings on the scene, and that the confrontation has been exposed in this way.