At least 78 people have died and dozens are feared missing after a fishing boat carrying migrants sank off the coast of southern Greece, authorities have said.

A large search and rescue operation has saved 104 people so far, four of whom have been taken to hospital with symptoms of hypothermia.

It was unclear how many passengers remained missing at sea after the Greek coast guard reported the 78 fatalities.

The incident took place last night around 45 miles south-west of Greece’s southern Peloponnese region.

Six coast guard vessels, a navy frigate, a military transport plane, an air force helicopter, several private vessels and a drone from the European Union border protection agency, Frontex, are taking part in the ongoing search.

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

The Italy-bound boat is believed to have sailed from the Tobruk area in eastern Libya.

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It comes as Libyan authorities launch a major crackdown on migrants, with several thousand – including Egyptians, Syrians, Sudanese and Pakistanis – detained.

Many Egyptians have been deported to their home country through a land crossing point.

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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.