Police arrested four suspected human traffickers and 29 undocumented immigrants in various parts of Attica on Saturday morning.
The migrants were found in a private coach that was stopped in Elefsina, west of Athens. The vehicle was bound for Italy, officers said.
They also stopped a car in Kolonos, near central Athens, and raided a property in Tavros, southern Athens.
Three of the four suspected smugglers are Indian and the fourth is Greek. Police said they are looking for two more Greeks and two more foreigners.