|The speech came as South Korea and the United States pressed on with their massive military drills on Monday [EPA]
The South Korean president has labelled North Korea's artillery attack on a southern island a crime against humanity and said Pyongyang will pay the price for any further provocation.
"North Korea will pay the price in the event of further provocations," President Lee Myung-bak said in an address on Monday.
"Attacking civilians militarily is an inhumane crime that is strictly forbidden in a time of war," he said.
North Korean shells rained down on Yeonpyeong island near the disputed maritime boundary and killed four people last Tuesday.
Amid criticism of the response to the attack, Lee has replaced his defence minister, ordered reinforcements for the 4,000 troops on Yeonpyeong and four other Yellow Sea islands and upgraded rules of engagement.
In his televised address on Monday, Lee apologised for failing to do enough to prevent the shelling.
"I feel deeply responsible for failing to protect my people's lives and property," he said.
Support for attack
A poll requested by the independent East Asia Institute think-tank showed 72 per cent of South Koreans surveyed thought the government response to the attack was inappropriate and 69 per cent supported a "restrained military attack".
That figure was up sharply from less than 30 per cent in a similar poll after the sinking of the Cheonan naval vessel in March, also blamed on the North.
Lee’s address came as South Korean and US forces pressed on with massive military drills on Monday, while regional powers considered a call by China for emergency talks.
China suggested talks between the six governments involved in stalled negotiations aimed at ending North Korea’s nuclear programme.
China's proposed emergency consultations came amid global pressure on Beijing to be more aggressive in helping resolve the stand-off between the rival Koreas and try to rein in ally Pyongyang which depends on China for aid.
Washington and Tokyo were non-committal, saying they would consult with Seoul, which was sceptical of the proposal to sit down with North Korea around a table, effectively rewarding it for bad behaviour.
The North was previously offered massive aid in return for disarmament pledges that went unmet.
"The six-party talks cannot substitute for action by North Korea to comply with its obligations," a state department spokesman said, referring to disarmament talks which North Korea abandoned two years ago.
"We have called on China to urge the DPRK (North Korea) to restrain its provocations and responsibly act in the interests of peace and stability."
The call for the two Koreas, the United States, Japan, and Russia to meet at a forum hosted by China must be reviewed "very cautiously" in view of North Korea's provocations, Seoul said.
Both Beijing and Pyongyang have been pressing regional powers to return to talks in some form or other for the past few months in a move analysts say is aimed at extracting concessions.
China, which agreed with South Korea that the situation was "worrisome", suggested the emergency talks for December. It did not say whether Pyongyang had agreed to join.