Authorities were searching for dozens of migrants missing from a sunken boat after Greece's coastguard rescued 29 in the Aegean Sea on Wednesday.

The rescued migrants said their boat had set out from Antalya, Turkey, heading towards Italy with 60 to 80 people aboard, according to a coastguard spokesperson.

It had capsized and sunk off the island of Karpathos, 38 nautical miles south of Rhodes. The search and rescue operation had begun in the early morning hours amid strong winds, coast guard officials said.

The navy and air force were assisting coast guard officials and at least six vessels and a Super Puma helicopter were taking part in the operation, with coast guard video showing some of the migrants being pulled up into the helicopter from the sea in darkness.

The rescued migrants were from Afghanistan, Iran and Iraq, another coastguard official said on condition of anonymity.

EU border agency Frontex detected 2,220 illegal crossings in June on the eastern Mediterreanean route.

Greece has been heavily guarding its sea and land borders against migrant flows. Turkey accuses it of pushing boats back into Turkish territorial waters, which Athens denies.

Greece was at the front line of a European migration crisis in 2015 and 2016, when a million refugees fleeing war and poverty in Syria, Iraq and Afghanistan arrived in the country, mainly via Turkey. Since then Ankara agreed with the European Union to stem flows to Greece.