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 metres above the water near a South Korean naval ship in seas southwest of the Korean Peninsula.
Japan Chief Cabinet Secretary Yoshihide Suga declined to comment on the details of the South Korean accusation but told reporters it was "essential that the Japanese and South Korean defense authorities try to communicate and promote better understanding."
"If such activity repeats again, our military will respond strongly based on our response rules."