A fishing boat crammed with migrants and refugees trying to reach Europe capsized and sank off the coast of Greece on Wednesday.

At least 78 people have died and many are missing in one of the worst disasters of its kind this year.

The coastguard, navy and merchant vessels, and aircraft have fanned out for a vast search and rescue operation.

It remains unclear how many people were missing, but some initial reports suggested hundreds may have been on board when the boat went down far from shore.

Authorities said 104 people were rescued after the sinking in international waters about 75km (45 miles) southwest of Greece’s southern Peloponnese peninsula. The spot is close to the deepest part of the Mediterranean Sea, and depths of up to 17,000 feet (5,200 metres) could hamper any effort to locate a sunken vessel.

At the port of Kalamata, about 70 exhausted survivors bedded down in sleeping bags and blankets provided by rescuers in a large warehouse, while paramedics set up tents.

The Italy-bound boat was believed to have left the Tobruk area in eastern Libya.

The route from North Africa to Italy through the central Mediterranean is the deadliest in the world, according to United Nations migration agency the International Organization for Migration, which has recorded more than 21,000 deaths and disappearances there since 2014.