At least 45 people, including 17 children, died in two separate incidents of boats smuggling refugees sinking off two Greek islands overnight into Friday. Dozens survived, and a search and rescue operation was underway for more potential survivors.

In the first incident, a wooden boat carrying 48 people sank in the early hours off the small islet of Farmakonissi in the eastern Aegean. Forty one of the passengers managed to make it to shore, while authorities recovered seven bodies — six children and one woman — from the sea.

A few hours later, a wooden sailboat carrying an undetermined number of people sank off the islet of Kalolimnos, to the south of Farmakonissi. Greece's coast guard said 38 people drowned in that incident.

Coast guard vessels, a helicopter and private boats were searching for additional survivors in addition to the 26 people already rescued. Authorities said the survivors' estimates of how many people had originally been on board varied from about 40 to 70, so it was unclear how many people were missing.

In October, the International Organization for Migration (IOM) warned that the crisis could turn “more deadly” as winter approached and temperatures dropped. An average of 4,500 people per day were entering the European Union via the Greek islands at the end of September.

Greece has become the main gateway for people fleeing war and poverty trying to reach the European Union. More than 800,000 entered Greece last year, mostly using unseaworthy boats to reach Greek islands from the nearby Turkish coast. Hundreds have died in the attempt.

In a deal struck at the end of November, Turkey promised to help stem the flow of refugees to Europe in return for cash, visas and renewed talks on joining the European Union.

Turkey is host to 2.2 million Syrians and has spent around $8.5 billion on feeding and housing them since the start of Syria's civil war nearly five years ago.

Al Jazeera and The Associated Press