North Korea denied Thursday it attacked a South Korean warship that sank near their border in March, offering to dispatch an "inspection group" to verify Seoul's conclusion that Pyongyang is to blame.
The communist state's National Defense Commission (NDC), the highest seat of power, also said in a statement released through official television that any sanctions or retaliation over the sinking would be met with "tough measures including an all-out war."
North Korea routinely warns of war for any act of punishment against it.
The North Korean reaction came in the middle of a news conference in Seoul by a multinational team of investigators announcing "overwhelming evidence" that blames a high-performance North Korean torpedo for splitting the ship and killing 46 seamen.
Coinciding with the conference, the White House said it backs the South Korean conclusion and "strongly condemns" the March 26 attack on the 1,200-ton South Korean warship, the Cheonan.
"They are pointing a dirty accusing finger at us like a thief," an unidentified spokesman for the NDC, headed by leader Kim Jong-il, said in a statement, claiming that its navy did not attack the ship.
Calling South Korean President Lee Myung-bak "a traitor," the North said the investigation was a "sheer fabrication" and offered to send a delegation of investigators to Seoul to verify the conclusion.
"We remind the group of traitors in advance that there should be not a shred of doubt about the material evidence to be produced before the inspection group," it said, warning of an "unlimited retaliatory blow, merciless strong physical blow" if South Korea responds with even a minor act of aggression on its territory.
South Korea plans to take the case to the U.N. Security Council. President Lee pledged Thursday to take resolute measures to make the communist regime "admit its wrongdoings through strong international cooperation."
The Cheonan sinking is suspected to be a North Korean retaliation for a naval skirmish in November last year.
That month, a North Korean patrol boat opened fire on a South Korean naval ship after crossing the Yellow Sea border, only to retreat in flames. The two sides collided in an exchange of gunfire twice before along the sea border in 1999 and 2002.