Article Posted on : - Nov 24, 2010

INCHEON, SOUTH KOREA (AP): South Korea's troops were on high alert Wednesday as their government exchanged threats with rival North Korea following a frightening military skirmish that ratcheted tensions on the peninsula to new extremes.

President Barack Obama reaffirmed Washington's pledges to protect ally Seoul after the North shelled a South Korean island near their disputed border, killing at least two marines and wounding civilians in what UN Secretary-General Ban Ki-moon called one of the "gravest incidents" since the end of the Korean War.

South Korea vowed retaliation and Wednesday said it would strengthen military forces in the disputed western waters near the island of Yeonpyeong and to halt aid to the communist North, while the North warned of more military strikes if the South encroaches on the maritime border by "even 0.001 millimeter."

South Korea sent two ships carrying 2,000 boxes of relief supplies to the stricken island Wednesday, Coast guard official Kim Dong-jin said.

He said that about 340 residents escaping the island were to arrive at the port city of Incheon aboard a Coast Guard ship around mid-afternoon.

Images released by the local government and obtained through YTN television showed people huddled in emergency shelters, children wrapped in blankets, rows of destroyed houses with collapsed walls, blown out windows and charred roofs.

A man with a shovel walked through the rubble.

The skirmish began Tuesday 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.

Two South Korean marines were killed in the shelling that also injured 15 troops and three civilians.

Officials in Seoul said there could be considerable North Korean casualties.

Shin Sung-hee, a fisherman, said he was mending his fishing net near a port on Yeonpyeong when he saw columns of black smoke and fire billowing from the hills.

"I couldn't think of anything. I just thought my wife would be in danger, so I rushed to my house," Shin said.

His wife, Lee Chun-ok, said that when she fled her partly collapsed house, she saw black smoke engulfing the town and fires erupting from nearby hills; a woman was crying on a bridge. Her husband ran over and told her they had to escape, so they ran to a port and managed to get on a ferry with several hundred other people.

The US government called the North's barrages an outrageous, unprovoked attack, but sought to avoid any escalation and did not reposition any of its 29,000 troops stationed in the South.

Obama was expected to telephone South Korean President Lee Myung-bak to discuss the issue.