Four migrants, three of them children, died Thursday near the Greek island of Lesvos after their boat collided with a Greek rescue vessel, the coastguard said.
Search crews recovered the bodies of a woman, two little girls and a baby while coastguard vessels continued to search for another four people believed to be missing from the crash, which was caught on AFP camera.
Another 31 people of undisclosed nationality were rescued, the coastguard said. Officials say an investigation was ordered to determine how the 30-metre (100-foot) patrol vessel collided with the migrant boat.
The coastguard said that according to initial findings, the migrant boat had apparently attempted to flee.
Dozens of migrants have died making the perilous Aegean Sea crossing from Turkey to Greece.
On Wednesday, a woman, a young girl and a baby died after their boat sank off Lesbos. The International Organization for Migration says more than 600,000 migrants have reached Europes shores since January, while more than 3,000 have died or gone missing.
More than 450,000 of the total have arrived in Greece, most of them fleeing the civil war in Syria.
Athens and the UN refugee agency have both called on the European Union to open up more legal channels for people fleeing war and persecution, so that they do not have to risk their lives to reach safety.