National shock at a ferry disaster that may have claimed the lives of hundreds of South Korean schoolchildren was mixed with fury Thursday at growing evidence that many passengers were denied a proper chance to escape the sinking vessel.

Multiple survivor testimony highlighted the fact that passengers were repeatedly told to stay in their seats or cabins when the ferry first ran into trouble on Wednesday morning.

Those who obeyed found their possible escape route severely compromised after the vessel suddenly listed sharply to the port side, triggering total panic.

One survivor named Kim Sung-Mook said he had struggled to rescue around 30 high school students unable to escape from a large, open hall on the fourth level of the ship.

"I couldn't even get into the hall because the whole thing was leaning over so badly," Kim said.

"The ship was going underwater and there was nothing for them to hold on to with their hands. They couldn't crawl up the floor, because it was wet and at such a sharp angle," he said.

Using a fire hose he managed to pull a few to safety, "but there were so many of them ... I couldn't help them all."

One student who was rescued said most passengers had remained in their seat for "30 to 40 minutes" after the ferry first foundered, in line with instructions they received from crew members and over the internal tannoy system.

"The message was repeated again and again: 'Stay put. Don't move'," said another survivor Huh Young-Ki.

"We we're asking ourselves: 'Shouldn't we move? Shouldn't we try and get out?' But the announcement was saying help would be there in 10 minutes," Huh told the News Y television channel.

'Most stayed put as they were told'

Discipline is strict in the South Korean education system and authority rarely flouted, leaving observers to conclude that most of the 375 high school students on the ferry, in their late teens, would have probably obeyed any official commands without question.

"If only we had been told to get out earlier, then more of us would have been able to jump into the sea," one student who managed to escape told the MBC TV channel.

"But most people just stayed put as they were told," she added.

Once the 6,825-tonne vessel Sewol had begun to list, it soon ended up at a 90 degree angle to the water, before inverting completely and sinking with only a small section of the keel showing above water.

With only 179 rescued so far, the fear is that most of the 287 still unaccounted for were trapped inside the ship as it submerged.

The suggestion that many more should have been able to escape has added to the anguish of the relatives of the missing, and fuelled public anger in a country unused to a disaster of this scale, especially involving its efficient, modern transport infrastructure.

Most South Koreans believe they have left the sort of accidents that regularly blight developing countries behind.

With the exception of a subway station fire in 2003 that claimed 192 lives, there have been no large-scale disasters in the past nearly two decades.

A Seoul department store collapsed in 1995, killing more than 500 people, while nearly 300 people died when a ferry capsized off the west coast in 1993.

'One man was screaming for help'

The captain of the Sewol, Lee Joon-Seok, was among those who escaped the ferry before it sank and was being questioned by investigators on Thursday.

Surrounded by TV cameras and reporters as he waited in the coastguard's southern headquarters in Mokpo, Lee pulled a hood over his head and face, and mumbled incoherently in response to persistent questions to explain what happened.

One 61-year-old woman escaped after ignoring the advice to stay in her cabin which she said was still being relayed as it filled with water.

"I swam for a while and then managed to crawl to an upper deck and then to a window where other people were clinging on," she told reporters in a hospital where she was recovering.

"One man was slamming on the window screaming for help, and then a rescue boat came up and they smashed the window in and pulled us out," she said.

Jin Kyo-Joong, the former chief of the South Korean Navy's ship salvage unit, said there were emergency situations where keeping passengers from moving was crucial.

"But if the ship is listing so dramatically to the point where people can't even move around, then ordering them to stay put is obviously the wrong order," Jin told the YTN television channel.