South Korean President Park Geun Hye turned on the captain and crew of the sunken ferry Sewol on Monday, saying publicly that they had exhibited "unforgivable, murderous behaviour."

Ms Park said at a cabinet briefing: "What the captain and part of the crew did is unfathomable from the viewpoint of common sense."

She said that instead of following a marine traffic controller's instructions the captain "told the passengers to stay put while they themselves became the first to escape."

"Legally and ethically," she added, "this is an unimaginable act."

The captain and two crew members have been arrested on suspicion of negligence and abandoning people in need, and prosecutors said yesterday that another four crew members have been detained.

Prosecutors will decide whether to proceed with charges against two first mates, a second mate and a chief engineer.