The one-year-old boy, whose nationality was not made known, was found unconscious on a rubber dinghy which had broken down and went adrift late on Thursday. The boy was taken to a hospital where he was pronounced dead.

The coastguard rescued the rest of the migrants, some of whom were in the sea.

The baby was one of thousands of refugees - mostly fleeing war-torn Syria, Afghanistanand Iraq - who attempt the short but perilous crossing from the Turkish coast to Greek islands by boat, often in rough seas.

Almost 400,000 people have arrived in Greece this year, the U.N. refugee agency UNHCR has said, overwhelming the crisis-stricken government's ability to cope. Most have rapidly headed north towards Germany.

The coastguard has rescued a total of 542 migrants and refugees off the Aegean islands of Lesbos, Chios, Samos, Farmakonisi and Agathonisi since early yesterday.