Another student said it appeared there were more fishermen involved in the rescue than coast guard. Like others, she said the crew should be punished severely for their actions.

South Korean ferry crew go on trial

"More than that, I want to know the fundamental reason why my friends had to end up like that," she said.

The six teenage survivors described how there were repeated orders not to move from their cabins. Orders to put on their life vests came much later and without any information about what was happening to the ship as it began to list sharply.

They were the first of 75 children who survived due to give evidence in the trial at the Gwangju court, which has been moved to Ansan south of Seoul to accommodate the students.

Five of them gave their evidence facing away from the court. One testified from another room via closed-circuit television.

The crew members on trial, including the captain, have said they thought it was the coast guard's job to evacuate passengers. Video footage of their escape triggered outrage across South Korea.

The government of President Park Geun-hye was heavily criticised over the slow and ineffective handling of the rescue operation. Park has vowed to break up the coast guard and streamline rescue operations, which are now split between the police, coast guard and others, into a single national agency.

The disaster also sparked South Korea's biggest manhunt as authorities searched for Yoo Byung-un, the man at the head of a family business that operated the doomed ferry.

Yoo's badly decomposed body was only identified last week after it was found by a farmer at an orchard last month.

Earlier on Monday, a close associate of Yoo, a woman identified by police only by her last name of Kim, was arrested after handing herself in. It was believed she helped him elude police after the disaster.

Another woman, the wife of Yoo's driver who was thought to have been with him during his final days at large, also turned herself in to police.

Kim's arrest came three days after police stormed an apartment on the outskirts of Seoul and found Yoo's elder son, Dae-gyun, who was wanted for embezzlement.

Yoo Dae-gyun was not believed to have been as actively involved in management of the family business as his younger brother, who is believed to be in the United States. He said he only learned of his father's death from police.

Extensive decomposition of Yoo Byung-un's body meant it was not possible to determine the cause of his death despite forensic and DNA tests, authorities said last week.