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 its northern rival 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 on Wednesday while hundreds of residents escaping the island were taken to the port city of Incheon aboard a coastguard ship.
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.