Nine security vehicles were burned in an arson attack early on Tuesday, after youths on motorcycles hurled petrol bombs into a parking lot, police said.
No one was injured in the Christmas morning attack, and no group claimed responsibility.
The vehicles were used by the Group 4 company, part of the British-based security giant G4S PLC.
Police said the incident occurred in the western Kolonos area of the city. They said witnesses saw youths throw petrol bombs into the parking lot.
Anarchist groups in the Greek capital frequently carry out arson attacks against government property and businesses that are part of international companies.