Three migrants died after a second boat sank off Greece days after a woman and four children drowned, the coastguard said on Tuesday.
More than a dozen people are missing after the dinghy they were travelling in hit rocks in high winds off the Greek island of Lesbos.
It comes two days after four migrants, including three children, died after their boat sank off the island of Leros in the south-eastern Aegean Sea.
The coastguard said 19 people were rescued in the operation which began in the early hours of Tuesday after an inflatable rubber boat was spotted on rocks.
At least 10 people were taken to hospital, authorities said, some suffering from hypothermia as a cold weather front brought freezing temperatures and snow across many parts of Greece this week.
None of the people on the dinghy had been given life jackets.
Survivors told authorities 41 people were on board the dinghy that had sailed from the Turkish coast. Two coast guard vessels and a Super Puma helicopter were assisting in the search operation amid strong winds, the coastguard said.
The migrants are understood to be from Syria, Yemen and Somalia.
Greece has long been one of the main entry points into the European Union for refugees and migrants from the Middle East, Africa and Asia.
More than 2,200 people fleeing war and poverty are known to have lost their lives in the eastern Mediterranean since 2014.
