Japanese Defense Minister Takeshi Iwaya said Friday a South Korean destroyer directed fire-control radar at a Maritime Self-Defense Force aircraft in the Sea of Japan the previous day, lodging a strong protest with Seoul.

"It was an extremely dangerous act that could cause a contingency situation," Iwaya told a press conference. "It's so regrettable and we demand that South Korea never let that happen again."

The radar was directed at an MSDF P-1 patrol aircraft within Japan's exclusive economic zone, but outside its territorial waters, off the coast of Ishikawa Prefecture, central Japan, at around 3 p.m. on Thursday, according to the Japanese Defense Ministry.

The incident is almost certain to add to bilateral tensions, with relations already hurt by recent rulings by South Korea's Supreme Court ordering major Japanese companies to pay compensation for wartime forced labor.

Iwaya said the South Korean side made no response to an inquiry from the patrol plane about the radar.

"It's impossible for a friendly country (to take such an action). I'm surprised," a senior Japanese Foreign Ministry official told reporters.

In January 2013, a Chinese warship directed fire-control radar against an MSDF vessel in the East China Sea, where Japan and China are involved in a dispute over the ownership of a group of uninhabited islands.