North Korea's military says it is planning to launch "special actions" meant to wipe out the administration of the South Korean president, Lee Myung-bak.
The army statement carried by state media on Monday said the actions would last three to four minutes and be carried out "by unprecedented peculiar means and methods of our own style". It gave no more details.
North Korea regularly criticises Seoul and just last week renewed its promise to wage a "sacred war", saying President Lee had insulted the 15 April celebrations to mark the birth centenary of North Korea's founder Kim Il-sung.
But Monday's statement was unusual in promising something soon and describing a specific length of time.
The threat follows UN condemnation of North Korea's launch of a long-range rocket which exploded shortly after liftoff on 13 April. Pyongyang said the launch was meant to put a satellite into orbit but Washington, Seoul and others condemned it as a cover for testing long-range missile technology.
North Korea's special actions would "reduce all the rat-like groups and the bases for provocations to ashes in three or four minutes, [or] in much shorter time, by unprecedented peculiar means and methods of our own style", according to the statement by the special operation action group of the Korean People's Army's Supreme Command.
Some South Korean analysts speculated that the statement was meant to unnerve Seoul; others that North Korea could be planning terrorist attacks.
It seemed unlikely that Pyongyang would launch a large-scale military attack against Seoul, which is backed by nearly 30,000 US troops stationed there, said Kim Young-soo, a professor at Sogang University in Seoul.
The animosity between the two countries has prompted worries that North Korea might conduct a new nuclear test – something it did after rocket launches in 2006 and 2009. South Korean intelligence officials have said that recent satellite images show North Korea has been digging a tunnel in what appears to be preparations for a third nuclear test.
South Korea's unification ministry said it was examining North Korea's intentions while the defence ministry said no special military movement had been observed in North Korea.
