Witness accounts suggested between 400 and 750 people had packed the 20- to 30 metre-long (65- to 100-foot) fishing boat that capsized and sank early on Wednesday morning about 50 miles (80 km) from the southern coastal town of Pylos.

In the immediate aftermath of the disaster 104 survivors and 78 people who drowned were brought to shore by Greek authorities, but nothing has been found since.

A massive search and rescue operation continued on Friday, but hopes were dwindling of finding any more survivors from the hundreds of people believed to have been on board the boat when it sank in some of the deepest waters of the Mediterranean.

Early Friday survivor Mohammad, 18, from Syria, burst into sobs as he spotted his elder brother Fadi, who travelled from the Netherlands searching for him.

They wept and hugged through metal barricades, erected by Greek police around a warehouse in Kalamata where survivors had been sleeping for the past two days.

"Thank God for your safety," Fadi said, repeatedly kissing his younger sibling on the head.

About 25 other relatives gathered outside hoping for news, clasping screenshots of their loved ones on mobiles phones.

Most of the survivors were later transferred by bus to a migrant camp in Malakasa, near Athens, on Friday. Others remained in hospital in Kalamata.

MIGRANTS HAD PAID $4,500

Pope Francis, who visited Greece two years ago to draw attention to the plight of refugees, urged for measures to prevent similar incidents in the future.

"I feel great pain at the death of the migrants, including many children, in the shipwreck in the Aegean Sea," he said on Twitter. "We must do everything possible so that migrants fleeing war and poverty do not meet death while seeking a future of hope."

The ageing fishing vessel was thought to have departed from Egypt, then picked up passengers in the Libyan coastal city of Tobruk on June 10. Greek authorities say survivors have told them they paid $4,500 each to go to Italy.

The exact circumstances of the vessel sinking while it was being shadowed by the Greek coastguard are still unclear.

Authorities, who were alerted by Italy on Tuesday and subsequently monitored the vessel over a period of 15 hours before it sank, say occupants on the vessel repeatedly refused Greek help, saying they wanted to go to Italy.

An advocacy group that had been in communication with the vessel said that on at least two occasions persons on board pleaded for help. The group, Alarm Phone, said it had alerted Greek authorities and aid agencies hours before the disaster unfolded.

'CURRENT APPROACH UNWORKABLE'

The International Organization for Migration (IOM) and the United Nation's refugee agency, the UNHCR, said the latest tragedy in the Mediterranean was the worst in several years and urged states to address the gaps in search and rescue rules.

"It is clear, that the current approach to the Mediterranean is unworkable," IOM's Federico Soda. "Year after year, it continues to be the most dangerous migration route in the world, with the highest fatality rate."

Greek authorities denied accounts that surfaced late on Thursday that the boat flipped after the coastguard attempted to tow it.

"There was no effort to tug the boat," coastguard spokesman Nikos Alexiou told state broadcaster ERT.

Nine Egyptians, aged between 20 and 40 years, were arrested over the shipwreck on Thursday evening. Authorities said they faced charges of negligent manslaughter, exposing lives to danger, causing a shipwreck and human trafficking.

They were expected to appear before a judge and respond to the accusations in the coming days.

Under a conservative government in power until last month, Greece took a tough stance on migration, building walled camps and boosting border controls.

The country is currently governed by a caretaker administration pending an election on June 25.