An unidentified object detected on military radars flying near the border with North Korea turned out to be a flock of birds, the Joint Chiefs of Staff said Monday, after the detection prompted fighter jets to scramble.

Earlier in the day, the JCS said that the military "is checking and taking measures after the military radar captured an unidentified object in the sky above the Demilitarized Zone in the central portion of the inter-Korean border in Gangwon Province at around 1 p.m.

The object was found some 4.5 kilometers above the ground, inside the no-fly zone that the two Koreas set up along the border under the inter-Korean military agreement signed in September last year, according to a JCS officer.

"Upon spotting that, the military deployed several jets in response, which later confirmed that the trace was made by around 20 birds, which were presumed to be wild geese," the officer said.

While scrambling the jets, the South Korean military sent a notification to North Korea via the inter-Korean military communication channel in accordance with the military pact in order to prevent any accidental clashes, he added.

The incident took place after the military has come under fire for its recent border security failure that allowed a North Korean boat with four North Koreans aboard to arrive undetected at South Korea's eastern port of Sokcho, Gangwon Province. (Yonhap)