Greek police vowed on Sunday not to relent in their efforts to evict undocumented immigrants after a sweep they said had netted 1130 in central Athens over the weekend.
Police said a total of 4900 people were rounded up in the capital on Saturday, of which 1130 were detained.
"The police operation to evict undocumented immigrants will continue," a statement said.
Operation Xenios Zeus, named after the king of the ancient Greek gods in his role as protector of guests, mobilised 2000 police in Athens and another 2500 on Greece's eastern border with Turkey.
Police spokesperson Christos Manouras said on Saturday that the operation was a necessity for debt-laden Greece's national survival.
"We must send the message that Greece cannot afford work and hospitality" to would-be immigrants, he said.
Located in the southeastern extremity of the European Union, Greece has become a popular transit point for migrants from Asia or Africa seeking to enter the bloc.
But as the country struggles with a crippling economic crisis and sweeping austerity cuts, social tensions are on the rise and the increase in undocumented immigrants has fuelled xenophobia and racist attacks.
For the first time in Greek political history, the country in June voted into parliament a neo-Nazi party, Golden Dawn, which has promised to purge the country of illegal migrants.
Current figures show Greece has about 800 000 legally-registered immigrants, while the number of those without papers is estimated at more than 350 000.
On Wednesday, police said they were tripling the number of guards along Greece's border with Turkey to 1800 to ward off any influx of Syrian refugees.