After an exchange of artillery fire between the two Koreas, Seoul and Washington have announced a new joint military drill. South Korea also warns North Korea that any further aggression will bring enormous retaliation. The bodies of two men were found Wednesday on Yeonpyeong island, bringing the death toll to four from Tuesday's attack.
Just after a phone call between U.S. President Barack Obama and South Korean President Lee Myung-back, the two countries announced a joint military exercise.
It is the first significant response to Tuesday's fatal shelling of a South Korean island.
U.S. Forces spokesman David Oten, in Seoul, says the four-day drill will begin Sunday and include the aircraft carrier U.S.S. George Washington in the Yellow Sea.
"This exercise is defensive in nature. While planned well before yesterday's unprovoked artillery attack, it demonstrates the strength of the alliance and our commitment to regional stability through deterrence. It is also designed to improve our military interoperability," he said.
Two South Korean marines and at least two residents of Yeonpyeong island died in the shelling.
The top U.S. commander in South Korea on Wednesday called on Pyongyang to halt its attacks, saying North Korea threatens peace and stability on the peninsula.
General Walter Sharp also heads the United Nations Command here. In that role he has ordered the U.N. command to investigate North Korea's shelling of Yeonpyeong island.
Tuesday's incident caused an uproar here. The Dong-A Ilbo paper says North Korea, as a mad dog, needs to be hit with a club. The Chosun Ilbo says North Korea has put a dagger to South Korea's throat and that calls for an immediate, stern and precise retaliation. The JoongAng newspaper terms the attack a national crisis.
Defense Minister Kim Tae-young faced withering criticism from lawmakers Wednesday.
During a parliamentary hearing, lawmaker Song Young-Sun, with the governing Grand National Party, chastised Kim for the response.
She questions why is the shelling merely being termed a provocation? She says bombing civilians is combat. If South Korean forces cannot anticipate and accurately keep track of how many shells fell then the whole military is useless, she complains.
The defense minister, who could barely get a sentence in, was peppered with angry questions from lawmakers about why it took 13 minutes to begin the counter-strike after North Korea began firing artillery shells at the island.
The artillery exchange on the disputed western frontier is one of the worst escalations since the 1953 armistice that halted the three-year Korean War.
There has never been a peace treaty and tension has peaked and ebbed in subsequent years.
Relations turned particularly tense earlier this year when a South Korean warship exploded and sank in the Yellow Sea. An international investigation concluded the Cheonan was hit by a North Korean torpedo. But Pyongyang says it was not responsible.
The former director of the two main U.S. intelligence agencies (the CIA and NSA), Michael Hayden, says the Cheonan sinking and the artillery firing may be related to the power succession in Pyongyang. Hayden says heir apparent Kim Jong Un may be trying to demonstrate power and compare himself to his grandfather, North Korea's founder, Kim Il Sun.
"Unless someone brings pressure to bear on them, and I frankly, I think, that someone has to be China, yes, I think there will be more provocations," he sid.
Hayden says Pyongyang's behavior might also be intended to get the United States and other nations to return to stalled negotiations about Pyongyang's nuclear programs.
North Korea blames the South for initiating Tuesday's hostilities - saying an annual South Korean live fire training exercise on the island was a provocative preparation for war.