Greece's coast guard says the bodies of six people have been recovered from the sea off a Greek island in the eastern Aegean following the sinking of a suspected migrant smuggling boat.

The bodies of four children, one man and one woman were recovered off the island of Agathonisi Saturday morning, the coast guard said. Three people — two women and a man — managed to reach the coast and alert authorities to the boat sinking.

The three told authorities they had been in a wooden boat carrying an estimated 21 people which sank, for reasons that were not immediately clear.

A massive search and rescue operation was underway involving three aircraft, Greek navy and coast guard vessels, a vessel from the European border agency Frontex and private boats.