The bodies of three people were recovered Wednesday near the Greek island of Folegandros, the coastguard said, with dozens more feared missing after a boat carrying migrants sank.
The coastguard said it had rescued 12 people in a dinghy, including children.
The bodies of three men have been found so far, with a large search operation ongoing.
The boat carrying the migrants -- which according to state TV ERT was likely sailing from Turkey to Italy -- experienced engine failure and sank, the coastguard said.
Of the 12 survivors, only two wore life jackets, AFP quoted it as saying.
There was also confusion about the exact number of people on the boat that sank.
Some survivors placed the number at 32, while others said as many as 50 were on board, a coastguard official told AFP.
Four coastguard vessels, three helicopters, a military transport plane, eight nearby ships and three private vessels were taking part in the search and rescue operation, the coastguard said.
The operation began late Tuesday, after the coastguard received information that a vessel carrying migrants had run into trouble and had started taking on water south of the island.
Those rescued -- seven Iraqis, three Syrians and two Egyptians -- were all transferred to the hospital on the island of Santorini.
Nearly one million people, mainly Syrian refugees, arrived in the EU in 2015 after crossing to Greek islands close to Turkey.
Scores of refugees and migrants have drowned in the Aegean Sea trying to make the perilous crossing.
About 8,500 asylum seekers have arrived in Greece this year, most of them through its northeastern land border with Turkey, according to data by the United Nations' refugee agency.
