Japanese Defence Minister Takeshi Iwaya “strongly protested” to South Korea on Friday after a South Korean destroyer locked its targeting radar on a Japanese surveillance plane.
Iwaya, speaking to reporters at his ministry, described the incident as an “extremely dangerous act that could cause an unexpected situation”.
There was no immediate reaction from South Korea.
“It’s extremely regrettable. We will urge South Korea to prevent a recurrence,” says Iwaya.
Fire control radar is used to pinpoint the location of the target for missiles or shells. Directing the radar at the target can be considered a step away from actual firing.
Iwaya said the South Korean destroyer directed the radar at a Japanese navy’s P-1 patrol plane, which was conducting surveillance off the Noto Peninsula in the Sea of Japan, at around 15:00pm on Thursday.
In early 2013 a Chinese vessel directed a similar radar at a Japanese navy ship, prompting Prime Minister Shinzo Abe tourge Beijing not to stoke tension over disputed East China Sea isles.
Relations between Japan and South Korea have cooled over a bitter history that includes Japan’s 1910-45 colonisation of the Korean peninsula, the forced mobilisation of labour at Japanese companies and the use of comfort women, Japan’s euphemism for girls and women, forced to work in its wartime brothels.
The rows over wartime history have long been a hurdle for relations between the neighbours at a time when there is a need for concerted efforts to dismantle North Korea’s nuclear and missile programmes.