North Korea's shelling of Yeonpyeong Island in November 2010. KCNA/Reuters

(VOVworld) – A spokesman for North Korea's National Defense Commission (NDC) described South Korea's live-firing drill on Monday as the "most vicious military provocation”, according to the state-run Korean Central News Agency (KCNA).

KCNA quoted an NDC spokesperson as warning that Seoul’s move could adversely affect the two Koreas’ upcoming talks.

Despite the North's warning of possible "merciless" retaliation, Seoul conducted the drill around front-line islands in the Yellow Sea to mark the anniversary of North Korea's shelling of one of the islands five years ago. The Republic of Korean defense ministry’s spokesperson Kim Min-soek said that this was a regular drill and that Seoul has vowed to hit back immediately if North Korea launches any provocative actions.