Greek authorities have arrested four Pakistani nationals accused of smuggling migrants and freed eight Syrians held captive in a house near Athens.
"The four arrested Pakistanis are members of a criminal organisation specialising in snatching and illegally smuggling migrants, who were kept captive and forced to pay money," police said in a statement on Sunday.
Police freed eight Syrian nationals from the house in Koropi, who were found chained and had been subjected to frequent beatings.
Only given scarce food and water, the Syrians were forced to communicate with relatives who had to make payments to the captors.
Authorities were alerted after two other Syrians managed to escape from the 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, while arrivals by sea have increased owing to stricter controls on the Greek-Turkish northern land border.
In November, authorities in western Greece arrested four people - three Greeks and a foreign national - after 12 migrants, including four children, drowned while trying to reach Italy in an eight-metre fibreglass boat.
