North Korea warned Saturday of "unpredictable consequences" if the United States and South Korea go ahead with naval exercises in the Yellow Sea, days after launching a deadly attack on the South.
The USS George Washington aircraft carrier and its battle group were planning four days of exercises with South Korea from Sunday as a show of force after Pyongyang stunned the world with its artillery strike.
The planned drill has also heightened tensions between Washington and Beijing, which regards the Yellow Sea as its own ancestral waters and has refrained from condemning its communist ally Pyongyang over Tuesday's attack.
Washington has stressed that the manoeuvre is "defensive in nature", was planned before North Korea's attack, and is not aimed against China.
But North Korea's official KCNA news agency issued an ominous warning: "If the US brings its carrier to the West Sea of Korea (Yellow Sea) at last, no one can predict the ensuing consequences."
Tuesday's attack -- the first shelling of civilians since the 1950-53 Korean war, which Pyongyang says was provoked by a South Korean military exercise -- has plunged the peninsula into its worst crisis in decades.
China's state councillor Dai Bingguo, the country's top foreign policymaker, travelled to Seoul on Saturday and held talks on the situation with South Korean Foreign Minister Kim Sung-hwan, Beijing's official news agency Xinhua reported.
Chinese Foreign Minister Yang Jiechi also held phone talks on Saturday with his Japanese and Russian counterparts.
The government of South Korean President Lee Myung-bak has come under intense pressure from the opposition, newspapers and veterans' groups to take a tougher line against the regime of Kim Jong-Il.
General Yoo Nak-Joon, the commander of South Korea's Marine Corps, grimly pledged to "repay North Korea a hundred- and thousand-fold" for the deaths of two marines, at their funeral ceremony televised nationwide.
"We'll engrave this outrage deep into our bones," he said.
Hundreds of mourners including the prime minister, marines and weeping relatives paid their last respects to Sergeant Suh Jung-Woo, 22, and Private Moon Kwang-Wook, 20, who died Tuesday along with two civilians.
They filed past their portraits to lay flowers and light incense at an altar decorated with white chrysanthemums, before three rifle shots echoed for their final salute and their bodies were buried at a national cemetery.
KCNA said two civilian deaths from Pyongyang's artillery strike were "if true... very regrettable" but charged they had been used as "human shields" by being placed near artillery positions.
Lee in a security meeting warned that "there is a possibility that North Korea might commit wayward acts during the exercise," according to Hong Sang-Pyo, senior secretary for public affairs at the presidential Blue House.
The newly named defence minister, Kim Kwan-Jin, had earlier pledged a tougher response in case of another North Korean attack, vowing that "we need to hit back multiple times as hard", a news report said.
Kim, 61, a former head of the Joint Chiefs of Staff, replaced Kim Tae-Young, who resigned over criticism that South Korea was too soft in its reply to the attack, firing artillery shells but not launching air strikes.
In Seoul, about 1,000 South Korean marine veterans held a rally, burning the North Korean flag and portraits of Kim Jong-Il and his son, the 27-year-old heir-apparent Kim Jong-Un.
One demonstrator, Lee Kwang-Sun, told AFP the elderly men in camouflage uniforms "are ready to rush to the frontline if we are asked to do so."
Many newspaper editorials demanded an urgent military overhaul.
The Korea JoongAng Daily said "the military's credibility and potency has become highly questionable as it scurries and scrambles in the face of bolder provocation from the North".
The Korea Herald said that "the South should secure overwhelming firepower and allow fighter jets to launch counter-attacks against the North's attacks".
The Korea Times argued that "the sacking of defence minister Kim Tae-Young should be the start of the wholesale revamping of the troubled military".
It added: "Without cheering soldiers amid reform, the nation will face the repetition of humiliation in the face of North Korea's military adventurism."