Police Free Syrians held by Pakistanis for ransom

"The four arrested Pakistanis are members of a criminal organization specializing in trafficking and snatching illegal migrants, who were kept captive and forced to pay money," police said in a statement.

Only given scarce food and water, the Syrians were forced to communicate with relatives who had to make payments (labor ransoms) to the captors.

Authorities were alerted after two other Syrians managed to escape from the ''slave'' house and seek help.

Greece is the main port of entry into the European Union for migrants and refugees fleeing war-torn or impoverished countries in Africa, the Middle East and the Indian subcontinent.

Refugee traffic has soared over the past year because of the ongoing war in Syria and other places that are ravished by war and smaller conflicts, while arrivals by sea have increased owing to stricter controls on the Greek-Turkish northern land border.