South Korean forces fired warning shots Wednesday at a suspected North Korean drone which flew over the border, a news report said, a week after a nuclear test by Pyongyang heightened tensions between the rival neighbours.
The drone then flew back to the other side of the heavily fortified border, the joint chiefs of staff said, according to Yonhap News Agency.
The South's forces fired about 20 machine gun rounds, the report said.
The encounter is not the first involving a drone on the Korean peninsula. In September 2014 a primitive drone found by a fisherman was thought to have come from the North.
Earlier Wednesday, South Korean President Park Geun Hye urged China to agree to stronger sanctions against North Korea following Pyongyang's nuclear test.
"China has a very important role to play," Park said in a speech in Seoul.
China - Pyongyang's biggest ally - has said it opposes North Korea's nuclear weapons programme, but Park said Beijing's position should be underscored through action.
Pyongyang says it detonated a hydrogen bomb on January 6. Other nations have since cast doubt on the claim, but the test nevertheless triggered worldwide outrage.
The UN Security Council pledged last week to take "significant measures" against North Korea and said it would begin working on a resolution in response to the test.