South Korean and North Korean troops have exchanged fire across the border, South Korean officials say.
North Korea fired two rounds towards a frontline unit and South Korean soldiers returned fire three times.
The shooting occurred in Hwacheon, about 90km north-east of the South's capital, Seoul, according to reports from South Korean TV.
Officials say it was not clear if North Korea's initial shots were a deliberate provocation.
The border between the two Koreas is one of the most heavily fortified in the world, with many thousands of troops stationed on either side of a demilitarised zone, the BBC reports.
There have been frequent incidents at sea, but this is believed to be the first cross-border shooting on land since 2006.