Photo/IllutrationSuh Wook, chief director of operations at South Korea's Joint Chiefs of Staff, speaks during a press conference at the Defense Ministry in Seoul on Jan. 23. (Yonhap via AP)

SEOUL--South Korea's military accused Japan of a "clear provocation" over what it said was a threatening low-altitude flight by a Japanese patrol plane over a South Korean warship on Wednesday.

Seoul's Joint Chiefs of Staff said the plane flew 60 to 70 meters above the water near a South Korean naval ship in seas southwest of the Korean Peninsula.

Seoul and Tokyo are key U.S. allies and close economic partners, but are currently locked in disputes over military issues and wartime history.

The announcement comes after a weekslong spat between the countries' militaries over Japanese allegations that a South Korean warship locked its fire-control radar on a Japanese patrol plane in December. South Korea's military denied the allegation and accused the plane of flying low over the warship, which was engaged in a rescue operation of a North Korean fishing boat.

JCS official Suh Wook said Wednesday's flight was the third time Japanese planes have flown low over South Korean warships since the December incident. It's considered highly unlikely that such encounters will lead to actual military skirmishes.

"The threatening low-altitude flight conducted today, despite our firm request to the Japanese government to ensure that (such flights) don't recur, is a clear provocation against the naval vessel of a friendly country and makes it impossible for us not to question Japan's intentions," Suh said in a statement. "If such activity repeats again, our military will respond strongly based on our response rules."

The disputes between the militaries have further strained relations between Seoul and Tokyo, which have sunk to their worst level in recent years over wartime history issues.