North Korea troops 'fire into South Korea'
North Korean troops have fired across the border into South Korean territory, reports say.
The shooting occurred in Hwacheon, some 90km (56 miles) north-east of the South's capital, Seoul, according to reports from South Korea's YTN TV.
Yonhap news agency said two shots were aimed at a South Korean military unit.
The Reuters news agency quoted a defence ministry official in Seoul as confirming that the shooting had taken place.
The news agency reports that South Korea's Joint Chief of Staff said that the two states had exchanged fire.
Media reports said North Korea had fired two rounds towards a frontline unit in Hwacheon, in the eastern province of Gangwon.
A Joint Chiefs of Staff spokesperson said that no South Koreans were hurt, AFP reports.
"There were no more shots afterwards. We are now closely watching their movements," the unnamed spokesperson said.
The BBC's John Sudworth, in Seoul, says that the exchange of fire appears to have been a small incident which did not cause any damage.
South Korea does not rule out that the initial shot from the northern side of the border was accidental rather than deliberate, our correspondent adds.
Tensions high The incident comes as Seoul prepares to host a meeting of world leaders from the G20 group of nations on 11 and 12 November.
The border between the two Koreas is one of the most heavily fortified in the world, with many thousands of troops station on either side of a demilitarised zone.
There have been frequent incidents at sea, but this is believed to be the first cross-border shooting on land since 2006.
Tensions between the two rivals have been high since the South accused the North of torpedoing one of its warships in March, with the loss of 46 lives. Pyongyang denies the charge.
Earlier on Friday the North warned that relations with its neighbour would face a "catastrophic impact" if South Korea continued to reject talks aimed at easing tension.
The first round of discussions in two years ended without progress in September after Seoul demanded an apology from Pyongyang for the warship sinking.