South Korea along with many Western leaders have been lining up to condemn the deadly attack on the Cheonan after a team of experts found what they believe is conclusive evidence of North Korea's involvement.
South Korean officials unveiled to journalists a piece of torpedo which they said was found near the two sections of the 1,200-ton ship in which 46 sailors died on March 26.
The ship went down in minutes after a violent explosion split the vessel in half. More than 55 sailors survived the sinking just more than 1 mile southwest of Baeknyeong Island near the de facto sea border with North Korea in the Yellow Sea.
The officials pointed to a small blue marking on the torpedo, on show in a glass-enclosed case, which they said was similar to markings found on other North Korean torpedoes.
Investigators also recovered a propeller from the torpedo, Yoon Duk-yong, the investigating committee's co-chairman, told journalists at a news conference. The fonts on the torpedo are the same as used by North Korea, Yoon said.
The committee believed the torpedo was fired by a small to mid-size submarine.
But North Korea's National Defense Commission immediately issued statements denying it had anything to do with the attack on the Cheonan, part of the South Korean "puppet navy," North Korea's government-run Central News Agency said.
The commission also called the investigating team's conclusions "reckless" and part of South Korea's "smear campaign" against North Korea. It said the report by the experts from the United States, Australia, Britain and Sweden a "fabrication."
China, one of North Korea's few allies, has urged restraint by the West but also made few comments on the issue since the attack. It has not condemned North Korea and issued a note of sympathy to the South Korean government over the sailors' deaths, albeit a month after the sinking.
South Korean President Lee Myung-bak has pledged to take "stern action" and said he would be taking the incident to the U.N. Security Council, of which China is a permanent member along with the United States.
U.N. Secretary General Ban Ki-moon said the report was "deeply troubling" and the U.S. administration described the sinking as an "act of aggression" that threatens peace in the region.
Britain, Australia and Japan also have expressed anger over the investigation team's findings and said the event has deepened mistrust toward North Korea.
Japan's Prime Minister Yukio Hatoyama called North Korea's action "unforgivable." Japan would back a U.N. Security Council resolution against North Korea should South Korea seek one, he said.
White House Press Secretary Robert Gibbs said President Obama spoke to President Lee, saying South Korea could count on U.S. support.
Gibbs said that belligerence towards its neighbors and defiance of the international community are signs of weakness, not strength.
U.S. Secretary of State Hillary Clinton plans to make an official visit to Seoul next week as part of a swing through Asia with stops in Japan and China.
While South Korea has spoken of taking tough measures against the north, it remains to be seen what can be done in retaliation, short of more economic embargo against a country that is already suffering financially.
Some analysts have suggested that the sinking may be the result of a power struggle within North Korea's ruling elite. The military may be flexing its muscles independently of the political leadership whose succession has been a source of speculation.
North Korea made an unexpected announcement this week that its Supreme People's Assembly, the nation's rubber stamp Parliament, will meet for an extraordinary session on June 7.
The assembly meets usually only once a year. Analysts have said the upcoming meeting might be to prepare responses to any moves by the south to isolate it over the Cheonan incident.
The meeting also might be to hand over more responsibilities to Kim Jong Un, the favored son of the aging and presumed ailing North Korean leader Kim Jong Il.