|The incident has sparked intense public speculation and conspiracy theories [Reuters]
Salvage teams have lifted a South Korean warship from the seabed near the disputed border with the North, three weeks after it went down following an unexplained explosion.
At least 46 people were believed to have been killed when the 1,200-tonne Cheonan split in half after an explosion during a routine patrol on March 26, but only two bodies had previously been recovered.
But after the stern section was brought to the surface by a giant floating crane on Thursday, KBS television aired footage aired footage of bodies being removed from the wreckage on stretchers.
The South Korean defence ministry said that 18 bodies had been recovered. More were expected to be found once the stern had arrived been transported to a naval base.
Efforts to locate the missing crew and salvage the Cheonan have been hindered by bad weather and heavy seas.
Officials hope that an examination of the stern section by more than 120 local experts, along with seven Americand and there Australians, will provide clues to the cause of the sinking.
Lee Myung-Bak, South Korea's president, has called for "a very objective investigation" whose findings cannot be disputed, and promised "stern measures" against whoever was to blame.
South Korean officials have said they will look into all possibilities including that the ship might have been struck by a North Korean torpedo or a mine left over from the 1950-53 Korean War.
Lee Hyun-yup, a marine engineering expert at Chungnam National University in
South Korea, said it could take years to find the exact cause.
He said in order to ascertain whether North Korea was involved, authorities have to look at the shape of broken ship parts and recover splinters of a torpedo or a sea mine, and determine whether the North had such weapons.
The disputed border area was the scene of deadly naval clashes between North and South Korea in 1999 and 2002 and a firefight last November, but Pyongyang has reportedly denied any involvement in the incident.
The salvage operation comes as tensions on the Korean peninsula have increased with the North freezing assets of a South Korean firm at a joint tourism project north of the border once hailed as a symbol of co-operation.
A senior US official also suggested on Wednesday that the sinking could have affected the chances of resuming talks of North Korea's nuclear disarmament, which have been suspended for more than a year.
"Let's find out what happened in the sinking of the corvette," Kurt Campbell, the US assistant secretary of state, said when asked by reporters about moves to revive the talks.
"At this juncture, we told our South Korean friends that our primary objective is to work with them on the recovery of the ship and at that point, we will be able to make some judgments about the way forward."
Last month's sinking was one of South Korea's worst naval disasters.
In 1974, a ship sank off the southeast coast in stormy weather, killing 159 sailors and coast guard personnel. In 1967, 39 sailors were killed by North Korean artillery.
The 1950-53 Korean War ended with an armistice, not a peace treaty, leaving the Koreas still technically at war.