SEOUL - The foreign minister of South Korea said Wednesday that "it's obvious" that one of its warships was sunk by a North Korean torpedo, adding that his country now has enough evidence of a military strike to seek action by the U.N. Security Council.

Foreign Minister Yu Myung-hwan's remarks were the first by a South Korean official to pin definitive blame on the government of Kim Jong Il for the March incident, which killed 46 sailors and sharply escalated tensions on the Korean Peninsula.

Yu spoke out a day before his government was to release the results of an investigation that U.S. and East Asian officials say has uncovered evidence that North Korea launched a torpedo that ripped apart the 1,200-ton Cheonan near a disputed sea border between the two nations.

Details of the investigation have dribbled out this week in government leaks to U.S. and South Korean media. It was reported Wednesday that investigators have concluded that North Korea attacked the warship with a Chinese-made torpedo. Recovered torpedo fragments are inscribed with Chinese and Russian script, reports said.

North Korea imported the weapon -- a heavy acoustic-homing torpedo known as a Yu-3G -- from China in the 1980s, government officials told Yonhap, the South Korean news agency. When the investigation's findings are released Thursday, there will be a computer simulation of a 550-pound warhead striking the Cheonan, Yonhap said.

Investigators found a serial number -- written in a font used in North Korea -- on torpedo propeller fragments retrieved near the sunken ship, and they found traces of explosives that are identical to explosives found seven years ago in a stray North Korean torpedo, government officials told South Korean media.

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