A major rescue operation was under way on Sunday for 13 people missing after a Comoros-flagged cargo ship sank in gale-force winds off the Greek Aegean island of Lesbos.

The coastguard said a navy helicopter picked up one crew member from the RAPTOR cargo ship,  who was taken to Lesbos General Hospital.

"He is in a state of shock", coastguard spokesman Nikos Alexiou told AFP, without providing further details.

The fate of the other 13 was not immediately clear.

Five cargo ships, three coast guard vessels, air force and navy helicopters as well as a navy frigate joined the rescue effort.

Authorities said the cargo ship, which was carrying 14 crew members and was loaded with salt, went down 4.5 nautical miles (8.3 kilometres) southwest of Lesbos, near the coast of Turkey, early Sunday.

The 106-metre ship, built in 1984, had sailed from Dekheila, Egypt, heading for Istanbul.

The Athens News Agency (ANA), quoting the vessel's operating company based in Lebanon, said the crew included 11 Egyptians, two Syrians and one Indian.

According to the authorities, the ship first reported a mechanical failure at seven am local time (0500 GMT).

At 8:20 am, the captain reported that the ship was listing, and activated the "mayday" distress signal before disappearing from the radar, Alexiou told AFP.

According to ANA, the heavily-laden vessel was believed to have taken on water in the hold due to strong waves, causing it to list and sink.

Ships remained docked across several parts of Greece over the weekend, with wind speeds reaching 9-10 on the Beaufort scale, or strong gale to storm force.

An emergency weather warning by the Hellenic National Meteorological Service (EMY) was upgraded on Saturday from "worsening weather" to "dangerous weather phenomena", as Storm Oliver (also called Bettina) moved from the Adriatic Sea toward Greece.

Earlier this month, a historic Greek warship was damaged by gale force winds after repeatedly hitting a dock.

The country has been struck by repeated flooding over recent months after facing a series of storms.

Central Greece was devastated in September by cataclysmic amounts of rain dumped by Storm Daniel, destroying crops and killing tens of thousands of farm animals across a wide area that is the heart of Greece's agricultural production.