North Korea says it has carried out a live-fire artillery drill simulating an attack on the official residence of the South Korean president.
The exercise was overseen by North leader Kim Jong-un, said the KCNA state news agency, who called on the military to be ready to "ruthlessly" destroy the government in South.
It is the latest in a series of angry gestures by Pyongyang.
The South's President Park Geun-Hye has ordered the army to be on alert.
But she said on Thursday that "reckless provocations will only become a path to self-destruction for the North Korean regime".
North Korea has been reacting after the UN imposed some of its toughest sanctions following its nuclear and long-range rocket tests.
Pyongyang has also been angered, as it is annually, by joint US-South Korean military exercises taking place south of the border.
Already known for vitriolic language, the KCNA report threatened to turn the South's presidential residence, known as the Blue House, into a "sea of flames and ashes", foreign media reports.