Four migrants died when their boat sank off the Greek island of Lesbos, Greece's coastguard said on Monday, adding seven had been rescued from the sea.
"We recovered four bodies; the rescue operation continues. We don't know if there were more people on the boat," a coastguard official said.
This is the second fatal incident involving migrants off Lesbos, near the Turkish coast, in October.
More than a million people are fleeing war
Greece was on the frontline of a 2015-16 migration crisis when more than a million people fleeing war and poverty in the Middle East and Africa crossed into Europe.
Migrant flows subsequently ebbed. But the country has toughened migration rules, following a resurgence of arrivals from Libya via the islands of Crete and Gavdos.
This is a developing story.