Residents near a Roma camp fired shots to intimidate police officers carrying out an inspection in the early hours of Thursday.
The officers of the OPKE crime prevention unit responded with gunfire to the threat from the rooftops of apartment buildings in the area around the camp in Ano Liosia, north of Athens.
The incident happened after the unit officers called on the driver and three passengers of a suspicious vehicle to submit to an inspection.
All four men were arrested, but no additional details have been released concerning the incident. There were no reports of injuries.