The 28-year-old victim and two friends were attacked on Sunday in Thessaloniki by around 15 to 20 PAOK fans armed with clubs, Greek police said.
The Bulgarians were beaten and the victim fell into the road where a car struck him. The two survivors of the attack suffered non-life-threatening injuries.
An autopsy is being carried out to determine if the victim was killed when run over by the car or whether he had already died before he was hit by the vehicle.
Police have detained 14 people in connection to the incident, but are still looking for the driver.
The three victims were fans of Bulgarian league club Botev Plovdiv, whose supporters are linked with the Thessaloniki-based team Aris.
Aris is PAOK’s biggest rival in the city. The Bulgarians attended the Aris-PAOK derby on Saturday, in which Aris beat PAOK 4-2.
Additional reporting by Associated Press
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