SEOUL (APP) – South Korea on Monday staged a major live-fire exercise near the disputed inter-Korean sea border despite North Korea’s warning of possible “merciless” retaliation, military officials said.

The drill was carried out around front-line islands in the Yellow Sea to mark the anniversary of North Korea’s deadly shelling of one of them five years ago, the South’s defence ministry said.

The attack on Yeonpyeong Island on November 23, 2010 killed four South Koreans including two civilians and sparked brief fears of full-scale war. It was one of the most serious border incidents since the 1950-1953 Korean War.

South Korea has in the past staged live-fire exercises near the Yellow Sea border around the time of the anniversary as a show of strength.