More than 340 migrants were rescued off the Greek island of Crete yesterday amid growing fears that traffickers are opening up more dangerous routes to Europe.

Four bodies were recovered in the Mediterranean south of the island after a fishing boat capsized, and around 100 more are feared dead.

It was not clear whether the boat had blown off course after setting off from North Africa or had left Turkey and was avoiding Nato patrols further north in the Aegean.

The rescue came a week after another boat was intercepted off the coast of Crete carrying 65 migrants from Syria, Afghanistan and Pakistan.

The Greek coastguard said the 80ft fishing boat at the centre of yesterday’s operation was found half-sunk about 75 nautical miles south of Crete in international waters.

Greece sent two patrol vessels, a military plane and three helicopters, while at least six passing ships, including a British cargo vessel, took part in the rescue. Coastguard spokesman Nikos Lagadianos said: ‘The information we have on the number of people on board the vessel is still unclear – we’ve heard that there were 400 or 500 people, but we cannot confirm that number.’

The authorities in southern Crete said sports halls on the island would be used to house survivors taken there.

The coastguard said 242 were also being taken to Italy on a merchant ship, while others were being transported to Egypt, Turkey and Malta.

Migrant smugglers have opted for more dangerous routes after the EU signed at £4.7billion agreement with Turkey in March for it to take back all those arriving on the Greek islands.

The short crossing from the Turkish coast to islands such as Lesbos and Kos was the preferred route for migrants heading to Europe until the deal came into force.

The agreement has led to a dramatic decrease in the number of people crossing.

The coastguard said it and the European border patrol agency Frontex had rescued 164 people in four separate incidents on Thursday off the islands of Lesbos and Chios. Before the EU-Turkey deal, thousands were arriving each day.

Migrants have instead been attempting the much longer and more dangerous crossing from North Africa towards Italy.

Most survivors yesterday were picked up by the Norwegian-flagged Clipper Hebe tanker and were being transported to the Sicilian port of Augusta in Italy. Others were to be taken to Egypt and Malta.

The coastguard said the search was continuing for others who may have been on board the fishing boat.

Mr Lagadianos said it would be ‘very difficult’ for divers to reach the capsized vessel, which is believed to have sunk, any time soon.

The International Organisation for Migration said its observations supported the theory of a possible new migrant route, reporting a ‘surge of new arrivals to Greece further south, on sea lanes connecting North Africa to the island of Crete’.