North Korea has rejected a report by multinational investigators that accuses Pyongyang of sinking a South Korean warship in March and killing 46 sailors.

The North Korean National Defense Commission described the findings of the international team, co-led by South Korea, as a "fabrication" and a "farce." It promised Thursday to respond to any South Korean retaliation for the sinking of the Cheonan with "all-out war."

Earlier Thursday, the South Korean co-director of the team said evidence overwhelmingly proves that a North Korean submarine fired a torpedo that triggered a massive underwater blast and caused the Cheonan to break apart.

The office of South Korean President Lee Myung-bak says he declared that Seoul will take "resolute counter-measures" against North Korea through international cooperation.

It quotes Mr. Lee as telling Australian Prime Minister Kevin Rudd that South Korea wants Pyongyang to admit to "wrongdoing" regarding the sinking.

The international investigators say fragments of a torpedo found near the site of the sinking are similar to parts of a North Korean torpedo propeller obtained years ago by South Korea.

The White House late Wednesday called the sinking an "act of aggression" that challenges international peace and violates the 1953 armistice ending the three-year-long Korean War.

The U.N. says Secretary-General Ban Ki-moon found the results of the investigation "deeply troubling."

The area where the South Korean ship sank is near a maritime border designated by the United Nations at the signing of the 1953 Korean armistice.  Pyongyang has never accepted the border as valid.  The two Koreas have fought three naval clashes in the area since 1999.

Japanese Prime Minister Yukio Hatoyama said North Korea's actions are unforgivable. Chief Cabinet Secretary Hirofumi Hirano told reporters Thursday the news would complicate efforts to resume the stalled six-nation negotiations on North Korea's nuclear program.

But Chinese Foreign Ministry spokesman Ma Zhaoxu urged both North and South Korea to exercise "restraint" during a press briefing in the Beijing. Chinese Vice Foreign Minister Cui Tiankai called the sinking of the Cheonan "unfortunate" in a separate press briefing Thursday.

Australian Prime Minister Kevin Rudd called the findings of South Korea's investigation "deeply disturbing" and said the international community must make an "appropriate response."

*Some information for this report was provided by AP, AFP and Reuters.