Up to 50 people are missing after a boat carrying migrants sank off the Greek island of Karpathos in the Aegean Sea, a coastguard official has said.

"According to the statements of 29 rescued people, there were 80 people on the boat, so up to 50 people are missing," he said.

The Greek coastguard is searching for the missing people following the shipwreck which happened after the boat left Turkey yesterday heading for Italy.

The rescue effort included four vessels that were already sailing in the southern Aegean, two coastguard patrol boats and a Greek air force helicopter.

However, strong winds of up to 50km/h were hampering the operation, coastguard spokesperson Nikos Kokalas told Skai radio.

Greece is often the country of choice for migrants fleeing Africa and the Middle East to try to reach a better life in the European Union.

Many come to Greece via Turkey over the narrow and perilous sea crossing separating the traditional enemies.

Sixty-four people have died in the eastern Mediterranean since January, the International Organization for Migration has said.

Eight people died off the Greek island of Mykonos on 19 June when 108 more were rescued, according to the UN migration body.

Athens says migrant arrival numbers have climbed this year and accuses Ankara of not doing enough to stop smugglers from sending them across the border - often in flimsy boats that make for dangerous journeys.

Turkey pledged under a 2016 deal to cut migrant numbers leaving its shores in return for financial aid from the European Union.

At the end of June, the EU urged Ankara to halt "violent and illegal expulsions" from its territory.

Charity groups and media accuse Athens of illegally turning back migrants, a charge Greece's conservative Greek government denies.