North Korea's military on Sunday warned it could bombard islands near the disputed Yellow Sea border with South Korea, accusing Seoul of planning a naval live-fire drill in the area.
The North's Western Sector Command warned residents of five islands to "evacuate to safe areas" before what it said was the scheduled start time of the exercise on Monday morning.
Pyongyang has taken a hostile tone towards Seoul since Kim Jong-Un, the youngest son of the late leader Kim Jong-Il, took over following the death of his father in December.
In a notice carried by Pyongyang's official news agency, the military said Seoul's government "should not forget the lesson" of the North's bombardment of Yeonpyeong island in November 2010, which killed four South Koreans.
"Once the group of traitors starts a reckless military provocation...the KPA (Korean People's Army) will promptly make merciless retaliatory strikes," it said.
The North frequently warns the South against conducting live-fire exercises near the sea border, but there have been no incidents since Yeonpyeong.