Bodies of civilians found after Korean shelling

The burnt bodies of two male civilians have been found on an island attacked by North Korea, South Korean officials said.

The two construction workers are believed to have been in their 60s. The discovery comes a day after a frightening military skirmish between the Koreas ratcheted tensions on the peninsula to new extremes.

North Korea's artillery attack on the small South Korean island of Yeonpyeong, near their disputed border, also killed at least two marines in what UN Secretary-General Ban Ki-moon called one of the "gravest incidents" since the end of the Korean War.

South Korea's troops are on high alert as the government exchanges threats with rival North Korea after the military skirmish that took tensions on the peninsula to new extremes.

US President Barack Obama reaffirmed Washington's pledges to protect its ally after the North shelled the island.

In a conversation with South Korean president Lee Myung-bak, Mr Obama said the US stood "shoulder to shoulder" with Seoul. The White House said the presidents agreed to hold combined military exercises and enhanced training in the days ahead.

South Korea vowed massive retaliation should North Korea attack again and said it would strengthen military forces in the disputed western waters near Yeonpyeong and halt aid to the communist North.

The North, in turn, warned of more military strikes if the South encroached on the maritime border by "even 0.001 millimetre".

South Korea sent two ships carrying 2,000 boxes of relief supplies to the stricken island today.

Hundreds of exhausted residents escaping the island were taken to the port city of Incheon aboard a coastguard ship, telling harrowing tales of the hour of destruction.

"I heard the sound of artillery, and I felt that something was flying over my head," said Lim Jung-eun, a 36-year-old housewife who escaped Yeonpyeong island with her three children, one of whom, a nine-month-old baby girl, she carried on her back. "Then the mountain caught on fire."

The South Korean coastguard said more than 500 people arrived on the first ships from the island. They were greeted with hugs and tears by family members at the port.

Some, mostly the elderly, were taken to a line of ambulances waiting nearby.

"Right after I saw the news, I called my daughter," said Chung Doo-sun, a 55-year-old man from nearby Gimpo city. "She was crying and told me the windows of her home were all shattered."

His son-in-law, a marine on the island, was not hurt and will stay on the island. Mr Chung said he only slept one hour because of worries about his daughter and grandchildren, who were also safe.

"I'll never allow my daughter and my grandchildren to go back to Yeonpyeong island," he said. "North Korea is so unpredictable."

In the crowd at the port was a 68-year-old South Korean man waiting for his 46-year-old son and his daughter-in-law.

"I'm always worried about my son, because North Korea has always committed provocation near the island," said the man, who would only identify himself by his family name Kim.

"North Korea has not changed at all," Kim said. He said he still holds bitter memories of the Korean War. "They are so cruel."

The clash began when North Korea warned the South to halt military drills near their sea border, according to South Korean officials.

When Seoul refused and began firing artillery into disputed waters - but away from the North Korean shore - the North retaliated by shelling Yeonpyeong, which houses South Korean military installations and a small civilian population.

Seoul responded by unleashing its own barrage from K-9 155mm self-propelled howitzers and scrambling fighter jets.