President expresses outrage over North Korea attack

South Korea's president took responsibility today for failing to protect his citizens from a deadly North Korean artillery attack, vowing tough consequences for any future aggression and expressing outrage over the "ruthlessness of the North Korean regime".

Lee Myung-bak's short speech to the country came as a nuclear-powered US supercarrier and a South Korean destroyer participated in joint military exercises, a united show of force nearly a week after an artillery barrage on Yeonpyeong island killed four, including two civilians.

Meanwhile a South Korean county designated the front-line island as "off-limits" to civilians - a decision could pave the way for the evacuation of about 300 remaining residents, journalists and officials.

Lim Byung-chan, a spokesman for Ongjin County, which governs the island, said the designation was issued at the request of South Korea's military. South Korea's Defence Ministry said it would discuss whether to carry out the evacuation.

Yesterday the ministry urged the media to leave the island and sent a ship to ferry them off, saying it could not guarantee their safety, but bad weather forced a cancellation.

Amid the heightened tension, classified US State Department documents leaked by online whistleblower WikiLeaks yesterday showed the US and South Korea discussing possible scenarios for reunification of the peninsula and American worry over Pyongyang's nuclear weapons programme.

Under pressure to take stronger action in dealing with the defiant North, Mr Lee lashed out at Pyongyang.

"Only a few meters away from where shells landed, there is a school where classes were going on," he said. "I am outraged by the ruthlessness of the North Korean regime, which is even indifferent to the lives of little children."

Mr Lee has come under withering criticism for what opponents have called lapses in South Korea's response to the attack. He has replaced his defense minister, ordered reinforcements for the 4,000 troops on Yeonpyeong and four other Yellow Sea islands and upgraded rules of engagement.

North Korea threatened another "merciless" attack as South Korean protesters begged Mr Lee to find a way to resolve the tension and restore peace.

Minutes after Mr Lee finished his speech, the North issued a fresh threat to attack South Korea and the US, calling the allies' joint war drills "yet another grave military provocation".

The manoeuvres were an "intentional plot" by the United States and South Korea to prepare for war against North Korea, Pyongyang's main Rodong Sinmun newspaper said.

The North would launch counter attacks without hesitation on South Korea and US forces if they engaged in provocation again, according to the commentary carried by the official Korean Central News Agency.

China, the North's only major ally, belatedly jumped into the fray with Beijing's top nuclear envoy, Wu Dawei, calling for an emergency meeting in early December among regional powers involved in nuclear disarmament talks, including North Korea.

But Seoul gave a cool response to the proposal, saying it should be "reviewed very carefully" in the light of North Korea's recent revelation of a new uranium-enrichment facility.

The troubled relations between the two Koreas, which fought a three-year war in the 1950s, have deteriorated steadily since Mr Lee's conservative government took power in 2008 with a tough new policy towards the North.

Eight months ago a South Korean warship went down in western waters, killing 46 sailors in the worst attack on the South Korean military since the Korean War.

Then, last Tuesday, North Korean troops showered artillery on Yeonpyeong, a South Korean-held island that houses military bases as well as a civilian population of 1,300 - an attack that marked a new level of hostility.