SEOUL (AFP) - South Korean President Park Geun Hye said on Monday that the behaviour of the captain and crew of the ferry that capsized five days ago with 476 people on board was unacceptable and "tantamount to murder".

"The actions of the captain and some crew members were utterly incomprehensible, unacceptable and tantamount to murder," the presidential Blue House quoted Ms Park as saying in a meeting with senior aides.

"Not only my heart, but the hearts of all South Koreans have been broken and filled with shock and anger," said Ms Park, who had been heckled on Thursday when she met relatives of the hundreds of passengers still missing - most of them schoolchildren.

The families have criticised the official response to the disaster, saying the initial rescue effort was inadequate and mismanaged.

Ms Park said it was increasingly clear that Captain Lee Joon Seok had unnecessarily delayed the evacuation of passengers as the ferry started sinking, and then "deserted them" by escaping first.

Lee was arrested on Saturday along with a helmsman and the ship's relatively inexperienced third officer, who was in charge of the bridge when the ship first ran into trouble.

"This is utterly unimaginable, legally and ethically," she said, adding that all parties to the disaster, from the owners, to the safety inspectors to the crew would be investigated and all those responsible would be held "criminally accountable".