South Korean warships have carried out live-fire drills in the Yellow Sea, less than a week after holding a large-scale exercise to mark the anniversary of a North Korean attack.

South Korean naval officials say the live-fire drills involved destroyers, frigates, patrol boats and high-speed boats.

Last week's show of force came on the one-year anniversary of the North's shelling of Yeonpyeong island, which killed four people.

It was the first North Korean shelling of a civilian-populated South Korean territory since the Korean War in the 1950s.

South Korean Prime Minister Kim Hwang-sik promised last week a tough response to any further attacks.

Pyongyang blames the South for the shelling, saying it was in response to a “provocative” South Korean military drill on the island.