South Korean President Park Geun-Hye has said that the captain and crew of a ferry that capsized with hundreds of children on board acted in a way “tantamount to murder,” as four more crew members were arrested and the death toll rose to 87.

Park’s denunciation, in which she vowed to hold all those responsible for the disaster “criminally accountable”, followed the release of a transcript showing the panic and indecision that paralysed decision-making on the bridge as the ship listed and sank Wednesday morning.

The confirmed death toll jumped to 87 as divers stepped up the recovery of bodies from inside the 6825-tonne Sewol, but 215 people remained unaccounted for.

“The actions of the captain and some crew members were utterly incomprehensible, unacceptable and tantamount to murder,” Park said 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 Park, who was 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.

The president 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 with most of his crew members.

“This is utterly unimaginable, legally and ethically,” she said.

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.

Three more officers and an engineer were detained by police on Monday and prosecutors said they could face similar charges of criminal negligence and deserting passengers.

A transcript of the final radio communications between the Sewol and marine traffic control suggested a scene of total confusion as the vessel listed sharply to one side.

In the end, the evacuation order was only given around 40 minutes after the ship ran into trouble, by which time it was listing so heavily that escape was almost impossible.

Lee has insisted he had acted in the passengers’ best interest, delaying the order to abandon ship because he feared people would be swept away and drowned.

The search for the 215 passengers that remain unaccounted for continues, with the US government contributing a Navy salvage ship to help with the hunt.

The 78-metre ship will assist more than 500 volunteer and military divers from across South Korea.

–with AAP