The bodies of 24 migrants, including 10 children, were discovered off the Greek island of Samos Thursday after their boat capsized, the Greek coastguard said.
Eleven people from a dinghy carrying 45 people were still listed as missing following the latest tragedy involving overladen migrant boats crossing the Aegean Sea from Turkey to Greece.
Ten people were rescued unharmed.
Authorities initially said they had found 12 bodies but the number rose quickly as rescuers combed the waters for the missing.
There were five boys and five girls among the victims, while 10 people were pulled from the water unharmed, but in a state of shock, a coastguard spokeswoman said.
The alert was raised by one of the survivors, who managed to swim to shore.
Greek ships and two vessels from the European border agency Frontex took part in the rescue operation.
There was no information yet on the migrants country of origin.
Despite wintry conditions, thousands of people fleeing war and poverty in the Middle East, Asia and Africa continue to make the treacherous sea journey to Europe, many paying with their lives.
Last week, 44 people drowned in a single day when three migrant boats ran into trouble in Greek waters.
On Wednesday, rescuers found the bodies of seven drowned migrants, including two children, after their boat sank off the Greek island of Kos.
The latest tragedy comes as swamped Greek authorities are under pressure from their European counterparts to staunch the migrant flow.
The European Commission on Wednesday hit out at Athens, saying it had seriously neglected its duty to protect the blocs frontiers and raising the prospect of other EU members imposing border controls for up to two years.
The UN says more than 46,000 migrants have arrived in Greece so far this year, with 200 people dying during the voyage.
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