A Syrian teenager who survived a shipwreck that killed at least 78 people off Greece was emotionally reunited with his elder brother on Friday, but there was no news for other relatives searching for loved ones.

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.

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

Most of the survivors, 71 people, were transferred on Friday by bus to the migrant camp of Malakasa, a gated facility with barbed wire fencing 40 km (25 miles) outside Athens.

"It's a tragedy," said Secretary General of the Syrian Association of Greece Anwar Bakri, standing outside the camp.