Eighteen migrants drowned when their boat overturned 26 miles (40 km) south of the tiny southern Greek island of Chrysi, a coast guard official said on Saturday, while two were rescued from the sea.

The boat was initially detected by a Turkish cargo ship, which contacted the Greek authorities.

The survivors were being taken to the island of Crete, the official added.

Greece was on the front line of a 2015-16 migration crisis when more than a million people from the Middle East and Africa crossed into Europe.

Flows have ebbed since then, but the last year has seen a steep rise in migrant boats, mainly from Libya, heading for Crete, Gavdos and Chrysi - the three Aegean islands nearest to the African coast. Fatal accidents remain common.