A rescue diver jumps into the water off Jindo island on Thursday to search for missing passengers from the sunken Sewol ferry. Photo: CFP

 Furious relatives of missing victims from South Korea's ferry disaster attacked a top coast guard official Thursday, accusing him of lying about efforts to retrieve bodies still trapped in the submerged vessel.

Around 20 relatives forced their way into the office of Choi Sang-hwan, the deputy director of the South Korean Coast Guard, and pulled him outside, ripping his shirt and punching and slapping him around the face and neck.

The relatives accused Choi of exaggerating the scale of the recovery effort, saying the scene they witnessed during a boat trip to the disaster site earlier Thursday did not match with his briefings.

The bereaved families have continually criticized what they see as delays in the rescue and recovery operation and a lack of committed resources.

The crowed held Choi until other officials arrived and then subjected them to a lengthy grilling on the recovery operation.

The confirmed death toll on Thursday stood at 171, but 131 were still missing as dive teams searched in near pitch-black conditions for bodies trapped in the ferry's interior.

More than a week after the Sewol capsized and sank with 476 people on board, most of them high school students, there is still widespread anger over the pace of the initial rescue effort.

Many relatives believe some of the victims may have survived for several days in trapped air pockets, but perished in the cold water after no rescue came.

As a result some have asked for autopsies to be performed, to see if it would be possible to determine the precise cause and time of death.

"We have received a number of enquiries about autopsies," said a member of the forensic team on Jindo island working on identifying the bodies recovered from the disaster site.

An official responsible for legal and medical issues at the emergency situation desk on Jindo said there was nothing to prevent families having an autopsy carried out.

"But to my knowledge, nobody has so far actually brought a body to the National Forensic Service to have this done," the official said.

The belief that some passengers might have survived the initial capsize was very strong in the days immediately after the Sewol sank on April 16

This was fuelled in part by fake postings on social network sites that claimed to be text messages from passengers begging to be rescued.

Some have suggested that the ferry did not take on sufficient ballast to counteract its cargo weight.

The ship capsized after executing a sharp turn, which may have triggered a shift in the cargo and caused the vessel to list beyond a critical point of return.

AFP