South Korea's president convened an emergency national security meeting Friday, a day after an official report concluded that North Korea was responsible for the deadly sinking of a naval patrol ship.
North Korea, for its part, spoke of war for a second straight day, while U.S. Secretary of State Hillary Rodham Clinton was on the way to the region and tensions on the Korean peninsula were expected to dominate her agenda.
South Korea accused North Korea on Thursday of sinking the patrol ship Cheonan with a torpedo in late March in what was the deadliest attack on the South since the Korean War ended in 1953.
President Lee Myung-bak convened a meeting of his National Security Council, said Nam Ki-myung, an assistant in the press office at the presidential Blue House, though she had no details as the meeting was under way.
The council consists of the prime minister, the foreign and defense ministers, the minister in charge of unification with North Korea and the chief of the National Intelligence Service.
Lee vowed Thursday to take "resolute countermeasures" against the North over the sinking. He was expected to give an address to the nation in coming days.
North Korea, which has denied any role in the sinking, said Friday it "will regard the present situation as the phase of war and decisively handle all matters arising in inter-Korean relations to cope with it."
The remarks were included in a statement by the Committee for the Peaceful Reunification of Korea, which is in charge of inter-Korean affairs and carried on the Korean Central News Agency.
The statement followed one by the country's military on Thursday that any retaliation over the sinking would mean "all-out war."
Meanwhile, Clinton, the top U.S. diplomat, was scheduled to begin a three-nation tour of the region with a visit to Japan later Friday. Besides Tokyo, she will visit China and South Korea.
Japan criticized the North on Thursday over the sinking, but China, Pyongyang's key ally, refrained from doing so, instead calling on all parties to "stay calm and exercise restraint."
Just hours before she departed, the White House called the ship sinking an "act of aggression." In a statement, officials called it "a challenge to international peace and security and ... a violation of the Armistice Agreement" that ended the Korean War.
Separately, the U.N. Command's Military Armistice Commission will soon launch an investigation into whether the North has violated the 1953 armistice, South Korea's Yonhap news agency reported Friday, citing an unnamed government source.
Should the findings prove true, the commission will suggest holding military talks with the North and strongly protest the violation, the report said.
The 1950-53 Korean War ended in a truce, rather than a peace treaty. The land border is the world's most heavily armed and the western sea border has been the site of several deadly naval clashes since 1999. The United States stations 28,500 troops in the South.
An international team of civilian and military investigators declared Thursday in that a North Korean submarine fired a homing torpedo at the Cheonan on March 26, ripping the 1,200-ton ship in two.
Fifty-eight sailors were rescued, but 46 died - South Korea's worst military disaster since a truce ended the three-year Korean War in 1953.
Torpedo fragments found on the seabed "perfectly match" the schematics of a North Korean-made torpedo Pyongyang has tried to sell abroad, chief investigator Yoon Duk-yong said. A serial number on one piece is consistent with markings from a North Korean torpedo that Seoul obtained years earlier, he said.
"The evidence points overwhelmingly to the conclusion that the torpedo was fired by a North Korean submarine," he said. "There is no other plausible explanation."
North Korean naval spokesman Col. Pak In Ho told broadcaster APTN in an exclusive interview in Pyongyang that the evidence was faked.
It remains unclear what steps South Korea will pursue against the North. Options include taking the issue to the U.N. Security Council, where North Korea has been previously sanctioned over nuclear and missile tests.
Military retaliation, however, is seen as too dangerous and not a serious option given the vulnerability of South Korea's capital, Seoul, and its 10 million some residents to North Korean artillery located just across the border.
U.S. troops in and around South Korea remained on the same level of alert, said Adm. Mike Mullen, chairman of the Joint Chiefs of Staff.
Carl Baker, an expert on Korean military relations at the Pacific Forum CSIS think-tank in Honolulu, said that military retaliation was not in the cards.
"I think that we need to be strategic about it in the sense that you can't just go back and do something as retaliation because that just sort of feeds the cycle and so that's not going to be useful," he said. "And I think all indications in the South Korean military is that they recognize that."
North Korea cries South Korea will be committing an "act of war" to pretty much everything, so it will be interesting to see what happens if the Armistice Commission decides N. Korea did violate the armistice. South Korea is definitely not going to react militarily because of Seoul (Seoul would pretty much be bombed into nonexistence), so I wonder what they'll do. China is definitely going to be a key player, and their call for both sides to "stay calm and exercise restraint" seems like its geared towards North Korea (I have no firm reasoning for why I think so; it just strikes me as a subtle way to tell North Korea to chill the fuck out without playing into North Korea's persecution complex.) I'm a lot more interested in how China reacts to everything than North Korea, just because China's the one most holding N. Korea in check.