Civilian bodies found after North Korea gunfire

The two building workers are believed to have been in their 60s.

The discovery came a day after a military skirmish between the Koreas took tensions on the peninsula to new extremes and drew criticism from world leaders.

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 United States Secretary-General Ban Ki-moon called one of the "gravest incidents" since the end of the Korean War.

South Korea's troops were on high alert as the government exchanges threats with rival North Korea and United States President Barack Obama reaffirmed Washington's pledges to protect its ally after the North shelled the island. A US war ship was on its way to the area to participate in combined military exercises after Mr Obama held talks with South Korean president Lee Myung-bak and agreed to hold enhanced training.

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 island yesterday as 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, who escaped with her three children, including a baby she carried on her back. "Then the mountain caught on fire."

The clash began when North Korea warned the South to halt military drills near the sea border. South Korea began firing artillery into disputed waters and the North then shelled Yeonpyeong.