North Korea has warned of "unprecedented" action against South Korea's ruling establishment, amid tough rhetoric between the two sides.
A special operation to begin "soon" would "reduce its target to ashes", the military said in a statement.
On Friday North Korea also held a rally calling for the death of South Korea's president, condemning his comments against the North.
Seoul said last week it had deployed more missiles against the North.
A defence ministry spokesman said the missiles had a range of 1,000km (625 miles) and could hit any of Pyongyang's nuclear or missile sites.
The North's statement directly criticised South Korean President Lee Myung-bak, the defence minister, analysts and "rat-like elements" including conservative broadcasters, who were accused of "destroying fair-minded public opinion."
The statement, which was read out on state television, said that "the special actions of our revolutionary armed forces will start soon to meet the reckless challenge of the group of traitors".
North Korean rhetoric has been getting sharper in recent days following its failed rocket on 13 April, reports the BBC's Lucy Williamson.
Originally posted by jredwood301
I have been following this north korea thing pretty close. And i got thinking about the latest failed missle (or rocket) launch. The first thing that raised a flag was NK admitting the failed launch. Normaly they claim everything they do to be a success. This next part is strictly a hypothesis. What if NK did this on purpose. Did they put an explosive in there to blow it up at a certain spot and elevation. Was this a test for an EMP over SK. If you look at some of the trajectory paths and the spot that the missle failed and switched the trajectory to go over SK it would have failed (exploded) in the middle of SK. And that is why NK claimed a failed launch and it was actually a success. Would like to here opinions on this hypothesis!!!!! My first post so dont beat me up to bad.