The tragedies, the deadliest so far reported in the Aegean in 2016, come as the EU seeks to push Turkey to halt the flow of migrants across its borders in exchange for financial help.
A spokesperson for the Turkish coastguard told AFP that the bodies of 36 migrants had been found, including 29 recovered by the Turkish gendarmerie and seven by the coastguard.
It was not immediately clear how many boats had sunk in the high seasonal winds although the Dogan news agency said at least two separate incidents were involved.
Two dozen migrants seeking to reach the Greek island of Lesbos set out before dawn aboard a rubber boat but it capsized in bad weather and high seas, the Dogan reported.
The bodies were found either washed up on the beach near the resort of Ayvalik or in the sea nearby, Dogan said. Eight more migrants had been rescued.
Among those found dead was a woman who was six months pregnant, Dogan said.
Drowned toddler becomes first 2016 migrant casualty in the Aegean
Images published by Dogan showed the corpses of children, fully dressed and wearing shoes, lying on the beach with their life jackets still on.
'Over million reach Europe'
Video footage showed Turkish security forces lifting other bodies from the waves in the shallows on the shore.
The deaths are the latest involving migrants fleeing war and misery in the hope of finding a new life in Europe.
The images of the small lifeless bodies on the sand echo those of three-year-old Syrian refugee Aylan Kurdi, pictures of whose corpse lying face-down on a Turkish beach in September 2015 spurred Europe into greater action on the migrant crisis.
A drowned two-year-old boy became the first known migrant casualty of the year on Saturday after the crowded dinghy he was travelling in slammed into rocks off Greece's Agathonisi island, the coastguard said.
Turkey, which is home to some 2.2 million refugees from Syria's civil war, has become a hub for migrants seeking to reach Europe, many of whom pay people smugglers thousands of dollars for the risky crossing.
The International Organization for Migration (IOM) said 1,004,356 migrants and refugees reached Europe in 2015, almost five times the previous year's total of 219,000.
The IOM also said Tuesday that 3,771 migrants and refugees died crossing the Mediterranean trying to reach Europe in 2015, making the past year the deadliest on record.
It said 77 percent of the deaths occurred in the central Mediterranean route mostly used by smugglers operating from Libyan shores. But it noted a surge in the numbers who died in the eastern Mediterranean around Turkey and Greece.
"In 2015, 21 percent of deaths occurred in the eastern Mediterranean compared to only 1 percent in 2014," the IOM said.
Ankara reached an agreement with the EU in November to stem the flow of refugees heading to Europe, in return for financial assistance.
18 migrants drown off Turkey in latest refugee tragedy
Brussels vowed to provide three billion euros ($3.2 billion) in cash as well as political concessions to Ankara in return for its cooperation in tackling Europe's worst migrant crisis since World War II.
But onset of winter and rougher sea conditions do not appear to have deterred the migrants, with boats still arriving on the Greek islands daily.
The IOM said it estimated that in the first three days of 2016 alone just over 5,000 migrants and refugees crossed into Greece.
Citizens of Syria and Afghanistan accounted for almost 80 percent of these migrants, with others coming from Iraq, Iran and the Palestinian territories, it said.
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