At least five migrants including three children, died Wednesday after four boats sank between Turkey and Greece, as rescue workers searched the sea for dozens more, the Greek coastguard said.
One of the boats had around 100 migrants aboard when it sank north of the Greek island of Lesbos, it said.
The new accidents brought to 34 the number of migrants found dead in Greek waters this month, according to an AFP tally based on data from Greek port police.
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 Office for Migration (IOM).
More than 3,200 people have died during these crossings, most of them children, the IOM says.
Also Wednesday, Europe's Operation Sophia rescued about 1,000 migrants from six dinghies and a fishing boat off the Libyan coast, the Italian coastguard said.
The rescues were carried out by Italian, British, Slovenian and German vessels, it said.
Operation Sophia, coordinated by Italy, was set up to arrest smugglers and seize their vessels as Europe tries to stem the flow of migrants making the perilous sea crossing.
All the rescued migrants are now headed to Italy, the Italian coastguard said.