ATHENS (Reuters) - Greece mounted a rescue operation on Friday for a cargo ship carrying about 400 migrants after it sent out a distress signal off the island of Crete, the coast guard said.

       The Greek coast guard quoted passengers as saying the Turkish-flagged vessel had sailed from Turkey, calling it "one of the largest search and rescue operations carried out in the eastern Mediterranean."

       Authorities said the ship was being taken to land but gave no further details. The nationalities of the passengers were not immediately made public.

       Greece is one of the main routes into the European Union for asylum-seekers arriving from Turkey. But the number of arrivals has fallen sharply since 2016 after the EU and Ankara agreed a deal to stop migrants from crossing to Greece.

       Nearly 1 million people, mainly Syrian refugees, arrived in the EU in 2015 after crossing to Greek islands close to Turkey. Since the Taliban takeover of Afghanistan in August, many EU states fear a replay of that crisis.

       On Tuesday, four migrants, three of them children, drowned after a boat in which they and 23 others were trying to cross from Turkey to Greece sank off the island of Chios.

       (Reporting by Karolina Tagaris; Editing by Mark Heinrich)