North Korea's military warned South Korea and the United States of "unprecedented nuclear strikes" over a report the two countries plan to prepare for possible instability in the totalitarian country.
The North routinely issues such warnings and officials in Seoul and Washington react calmly. Diplomats in South Korea and the US instead have repeatedly called on Pyongyang to return to international negotiations aimed at ending its nuclear programs.
"Those who seek to bring down the system in the (North), whether they play a main role or a passive role, will fall victim to the unprecedented nuclear strikes of the invincible army," North Korea's military said in comments carried by the official Korean Central News Agency.
The North, believed have enough weaponized plutonium for at least half a dozen atomic bombs, conducted its second atomic test last year, drawing tighter UN sanctions.
Experts from South Korea, the US and China will meet in China next month to share information on North Korea, assess possible contingencies in the country, and consider ways to co-operate in case of an emergency situation, South Korea's Dong-a Ilbo newspaper reported earlier this month, citing unidentified sources in Seoul and Beijing. The experts will also hold follow-up meetings in Seoul in June and in Honolulu in July, it said.
The North Korean statement Friday specifically referred to the March 19 newspaper report.
A spokeswoman said the South Korean Defense Ministry had no information.
South Korean media have reported that Seoul has drawn up a military operations plan with the United States to cope with possible emergencies in the North. The North says the US plots to topple its regime, a claim Washington has consistently denied.
Last month, the North also threatened a "powerful - even nuclear - attack," if the US and South Korea went ahead with annual military drills. There was no military provocation from North Korea during the exercises.
China, Japan, Russia, South Korea and the US have been trying to persuade North Korea to give up its nuclear weapons in six party talks. The North quit the negotiations last year.
The fate of the North's nuclear weapons has taken on added urgency since late 2008 as concerns over the health of leader Kim Jong Il have intensified.
Kim, who suffered an apparent stroke in 2008, may die within three years, South Korean media have reported. His death is thought to have the potential to trigger instability and a power struggle in the North.