Soldiers from North and South Korea are said to have exchanged gunfire along the military border.
It’s the latest in a series of confrontations between the two rival nations.
According to the South Korean government, the North’s soldiers approached the frontier and when the South fired warning shots they didn’t retreat – they fired back.
No damage or casualties were reported but Seoul says it’s putting Pyongyang on alert.
“We gravely warn North Korea to stop immediately this reckless military provocation creating tension and violating the armistice agreement,” said South Korean Defence Ministry spokesman Kim Min-Seok.
Earlier this month gunfire was exchanged when a North Korean patrol boat crossed a sea border – and after southern activists sent a balloon into the North to release propaganda leaflets.
Experts say the North often engages in sabre-rattling to seek political advantage. Another-top level meeting between the two Koreas is expected soon.