At least 26 refugees, among them 17 children, drowned overnight when three boats sank off the islands of Kalymnos and Rhodes, Greek port officials and Turkish media said Friday.
The latest drownings prompted a sharp response from Greek Prime Minister Alexis Tsipras who said he felt "shame" over Europe's failure to prevent the tragedies.
Another 138 people were pulled to safety although the coastguard were continuing their search for survivors, officials said. Off Kalymnos, authorities recovered 19 bodies on Friday morning, among them six women and 10 children.
Further south, a woman, a child and baby drowned when another boat sank off Rhodes. Three people who had been on board with them were still missing early Friday, while six others were rescued.
In a third incident, four Syrian children drowned off the coast of Turkey on Friday when the flimsy boat carrying them to Greece capsized in bad weather, Turkish media reported.
Nearly 600 people were rescued by the coast guard in the past 24 hours, while thousands more made it safely to the islands.
And early on Friday, another boat was seen foundering off the coast of Lesbos, with a group of desperate people perched on the roof screaming for help.
The latest deaths came after a string of drownings off the tourist islands of Lesbos and Samos on Wednesday, with the latest figures showing at least 17 people, including 11 children, died.
Throughout October, 68 people have drowned while trying to reach Greece from Turkey, according to an AFP count based on statistics released by Greek port authorities.
Faced with yet another "humanitarian tragedy," Tsipras said it was crucial to prevent the Aegean Sea from becoming a graveyard for people fleeing war and misery and seeking safety in northern Europe.
"As a European leader, I feel shame over Europe's inability to defend its values," Tsipras told the Greek parliament. "Our first duty is to save lives and not to allow the Aegean to become a cemetery ... for that we are not asking for even a euro from our European partners."
He also underlined the urgent need of having Turkey "respect its commitments" to halting the flow of people leaving its territory by boat and stressing Athens' willingness to be "a link between the EU and Turkey" on the matter.
With the winter weather whipping up gales and worsening conditions at sea, the UN refugee agency (UNHCR) said there was an "urgent need" to strengthen search and rescue capacity in the area.
"We have warned for weeks that an already bad situation could get even worse if desperate refugees and migrants must continue to resort to smugglers who send them out to sea despite the worsening weather," said Alessandra Morelli, UNHCR's Senior Operations Coordinator for Greece in a statement released on Thursday. "Our fears are now being realized. Nearly every day now we are seeing children, parents, the elderly and the young dying as they try to reach Europe."
Since the start of the year, 560,000 migrants and refugees have arrived in Greece by sea, out of over 700,000 who have reached Europe via the Mediterranean, according to the International Organization for Migration (IOM).
Greece is the main point of entry for people fleeing war and poverty in the Middle East and Africa and seeking a better life in Europe, after an alternative sea route from Libya to Italy became too dangerous. Well over half a million — mainly Syrians and Afghans — have arrived so far this year from the nearby Turkish coast, as European governments weigh taking tougher measures to try to limit the number of arrivals in Europe.
The influx has overwhelmed authorities in Greece, which is struggling through its worst financial crisis in decades. More than 3,200 people have died during the perilous crossings although most of the deaths have occurred on the longer sea route from Libya to Italy.