At least 78 migrants dead and dozens feared missing after fishing vessel sinks off Greece

Survivors receive first aid after a rescue operation at the port in Kalamata town, about 240 kilometers (150miles) southwest of Athens on Wednesday. (AP)

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.

At the southern port of Kalamata, dozens of rescued migrants were taken to sheltered areas set up by the ambulance services and the United Nations Refugee Agency to receive dry clothes and medical attention.

Libyan authorities have launched a major crackdown on migrants earlier this month across eastern Libya. Activists have said several thousand migrants, including Egyptians, Syrians, Sudanese and Pakistanis, have been detained. Libyan authorities deported many Egyptians to their home country through a land crossing point.

In western Libya, authorities have raided migrant hubs in the capital, Tripoli, and other towns over the past few weeks. At least 1,800 migrants were detained and taken to government-run detention centres, according to the UN refugee agency.

Mediterranean 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 Wednesday, a yacht with 81 migrants on board was towed to a port on the south coast of Greece’s island of Crete after authorities received a distress call.