North Korean soldiers have boasted on state television of the attack on South Korea, saying it was immediate retaliation after the South fired first.
Tensions have been high since the November 23 artillery shelling killed four South Koreans. The South says a firing drill being conducted at the time aimed away from the border and should not have provoked an attack.
The soldiers spoke on a programme marking Saturday’s 19th anniversary of leader Kim Jong Il’s appointment as the North’s military commander.
Soldier Kim Moon Chol said: “Our eyes were full of fire right after we saw the enemy’s shells being fired into our sacred waters.”
Another soldier, Kim Kyong Su, said the North’s strike showed “no mercy at all”.