At least 22 undocumented immigrants, including three children, were killed Monday while 12 others are still missing after a sail boat capsized off eastern Greece, Greek Coast Guard officials said.
Thirty-six survivors have been rescued from the sea and the search is continuing, officials say.
Authorities say they do not yet know the nationalities of the migrants.
Coast guard vessels, a cruise liner and search and rescue helicopters were used in the recovery operation.
Thousands of migrants from Africa, Asia and the Middle East often pack into unsafe boats in attempts to get into the European Union. Fatal accidents are frequent.
Greece, Italy and Malta have repeatedly asked their EU partners to do more to help them handle the large number of migrants.
Greece is a major entry point for migrants and refugees trying to reach the European Union. Many cross by sea from Turkey, and accidents are frequent.