North Korea has sharply criticized South Korea for conducting military exercises Wednesday near an island just south of the contested Yellow Sea border.
North Korean state media quoted the country's supreme military command as saying the major drill represented a new political and military provocation. It threatened a "sea of fire" in Seoul if any future drill violates its territory.
Wednesday's drill involved South Korean aircraft, rocket launchers and artillery guns and took place off Baengnyeong Island, one of a number of so-called "front-line" islands in waters both Koreas claim as their territory.
No live-fire activities took place.
Officials in Seoul said the drill was meant to send a strong message to North Korean rivals stationed within sight just kilometers away.
The exercise marked the first anniversary on North Korea's artillery attack on the South Korean island of Yeonpyeong that killed two marines and two civilians.
Pyongyang says it shelled Yeonpyeong island on November 23, 2010, in retaliation for an artillery drill by the South on the island that sent shells into the North's maritime border.
The new North Korean military threat comes despite recent signs that animosities between the two nations are easing.
Some information for this report was provided by AP and AFP.