Seoul's foreign minister said Wednesday it was "obvious" North Korea was to blame for the sinking of a South Korean warship, and there was enough evidence to take the case to the UN Security Council.
The comments by Yu Myung-Hwan came a day before a multinational investigation team announces its report on the March 26 tragedy, which cost 46 lives.
Top South Korean officials had previously hinted strongly that the North was involved in the sinking of the 1,200-tonne corvette near the disputed border on March 26.
|A South Korean soldier stands guard at a check point during an anti-terror drill close to Seoul.|
But Yu was the first publicly to implicate the communist state, which denies involvement.
Asked by reporters whether the North had sunk the Cheonan, Yu replied: "I think it's obvious." Seoul has "enough evidence" to bring the issue to the UN, he added.
News reports said investigators had found a torpedo fragment with a serial number written in North Korean style.
The discovery, if confirmed, would be the latest and strongest piece of evidence that a North Korean torpedo broke the ship in two.
Yonhap news agency, citing unnamed military officials, said Seoul had collected a sizeable piece, presumed to be part of the axle of a torpedo, with a serial number written in a North Korean font.
It said this was in addition to a piece of the propeller salvaged earlier.
Chosun Ilbo newspaper carried a similar report.
"Analysing the serial number, experts from the US, Australia and other countries agree that the torpedo that sank the Cheonan must have been made by North Korea," an unnamed source told the paper.
"It is the smoking gun, following the discovery of a piece of torpedo and traces of explosive."
The defence ministry declined comment.
On Tuesday Yonhap said explosive traces found on the Cheonan and on the seabed have a similar chemical make-up to substances found in a stray North Korean torpedo secured by the South seven years ago.
Yu said in a speech on Wednesday that investigators, including experts from Britain, Sweden, the United States and Australia, have confirmed the corvette was hit by a torpedo.
Seoul would take "firm and prudent" measures to deter "any future provocations which will undermine peace and stability in Northeast Asia," he told the European Union Chamber of Commerce, appealing for international support.
In search of that backing, the foreign ministry Wednesday briefed diplomats from some 30 countries about the findings of the investigation. Envoys from China, Japan and Russia had been briefed a day earlier.
South Korea is likely to ask the UN Security Council to slap new sanctions on the North, in addition to those imposed to curb its missile and nuclear programmes.
But China, a veto-wielding council member and the North's ally, is unlikely to support new measures unless the South produces solid proof linking its neighbour to the attack.
The United States, which has 28,500 troops stationed in the South, has given its ally strong backing.
US President Barack Obama and South Korea's President Lee Myung-Bak, in a telephone conversation Monday, called on the North to end "belligerent behaviour towards its neighbours".
They stopped short of blaming it for the sinking but said they are committed "to follow the facts of the investigation wherever they lead."
Secretary of State Hillary Clinton will visit Seoul next week in a further demonstration of support.