Seoul warning on eve of war games

South Korea has vowed to "completely punish" North Korea if it attacks again, and has mobilised hundreds of troops, tanks and helicopters for a massive military exercise.

The firing drills planned for today near the heavily armed border signalled that South Korea is willing to risk escalating tensions with North Korea.

"We will completely punish the enemy if it provokes us again like the shelling of Yeonpyeong Island," said General Ju Eun-sik, chief of the army's 1st Armoured Brigade.