ATHENS — Coast guard, navy and merchant vessels and aircraft carried out a vast search-and-rescue operation into the early hours of Thursday morning for any migrants who may have survived the sinking of an overcrowded fishing boat off the Greek coast.

As the enormity of the tragedy became clear -- at least 79 dead and hundreds more thought to be missing -- residents in the southern city of Kalamata have been trying to help the survivors.

"The community has mobilized," said Athanasios Vasillopoulos, the Mayor of Kalamata.

"We have made food available as the local authority but many organizations have also brought food for these people. And many residents have called me offering to bring us whatever these people need. Everyone has reacted positively."

The shipwreck is the deadliest off Greek shores this year, prompting Greek caretaker Prime Minister Iaoannis Sarmas to declare three days of mourning.

"When these things happen our thoughts are with these people. We don't want people dying here or anywhere else," Kalamata resident, Gioli Kambouropoulou told Euronews.

"These people have the right to come to us and to Europe and we should take care of them. It's unbelievable how this happened with only 2 bf (Beaufort wind scale) of wind. I hope for more survivors and that we will help them any way we can," she added.

The Greek coast guard said survivors included 30 people from Egypt, 10 from Pakistan, 35 from Syria and two Palestinians.

It was unclear how many passengers were missing, but some initial reports suggested hundreds of people may have been aboard when the boat went down far from shore.

The Italy-bound boat is believed to have sailed from the Tobruk area in eastern Libya. The Italian coast guard first alerted Greek authorities and Frontex about the approaching vessel on Tuesday.

Smugglers are increasingly taking larger boats into international waters off the Greek mainland to try to avoid local coast guard patrols.

On Sunday, 90 migrants on a US-flagged yacht were rescued in the area after they made a distress call.

Separately on Wednesday, a yacht with more than 70 migrants on board was towed to a port on the south coast of Greece's island of Crete after authorities received a distress call. — Euronews