North Korean leader Kim Jong-un warned the South would "regret bitterly" any incursion of their disputed sea border as he directed a large-scale mock assault on an island, state media reported yesterday.
The joint landing drill involving the army, navy and air force followed a series of missile tests in the past week - seen by some as a display of pique over President Xi Jinping's two-day state visit to Seoul.
The mock assault is apparently aimed at five islands controlled by the South near the southwestern part of North Korea. Seoul suspects the islands, which provide outposts for the South, will be the first target for the North in the case of an armed conflict.
"Participating in the drill were combatants, artillery pieces of various calibres, combat ships including submarines, and formations of pursuit fighters, bombers and transport planes of units," the North's Korean Central News Agency said.
Kim watched the North Korean forces successively pound the mock enemy positions through "the well-organised coordinated operation as required by the modern warfare", and "deadly firepower strikes" on the island were followed by infantry landings and paratroops.
The agency did not give the venue of the exercise, which apparently took place on Friday as Xi wrapped up his visit to Seoul.
Kim said the North's southwestern waters were exposed to "frequent threats" from the South, repeating Pyongyang's allegations that shells fired by the South dropped in the North's territorial waters some days ago.
The agency said Kim took the matter very seriously and "strongly warned" that "should the enemies repeat the wrong choice on the wrong day in the hotspot waters, he would make them regret bitterly".
Kim was apparently referring to a live-fire exercise last month by South Korean marines based on islands near the disputed western sea border.
Xi's decision to visit Seoul before Pyongyang was seen as a pointed snub to North Korea, with Beijing's patience over its wayward ally's nuclear brinksmanship wearing thin.
Kim is still waiting for an invitation to Beijing.