South Korean soldiers fired warning shots at a suspected North Korean drone on Wednesday that crossed the tense border, the defence ministry said.
The unidentified aerial vehicle flew across the border and encroached into South Korean territory by some "tens of metres (yards)", the defence ministry said.
The incursion occurred near South Korea's Mount Dora Observation Post, some 47 kilometres (29 miles) north of Seoul, at 2:10 pm (05:10 GMT).
South Korean soldiers responded by sounding broadcasts and firing warning shots before "the vehicle immediately returned to the north," the ministry said.
Yonhap news agency said about 20 rounds had been fired as warning shots from a machine gun.
South Korea's President Park Geun-hye answers a reporter's question during her New Year news conference at the Presidential Blue House in Seoul
