Three unidentified persons, believed by police to be Olympiakos Piraeus (OSFP) supporters, opened fire with a Kalashnikov against a group of 7 Panathinaikos (PAO) fans, injuring two of them, aged 27 and 28, in the legs.
The incident was in follow-up to an earlier incident outside an Olympiakos fan club in Corinth when, after the PAO basketball team qualified for the Final Four in Barcelona, a group of celebrating PAO fans went to the OSFP fan club and scuffled with Olympiakos supporters.
Police arrived on the scene and broke up the crowd, but the two sides gave a "rendezvous" for a rumble later to "settle their differences".
Seven of the PAO fans showed up at the meeting place and were shot at by three other youths that also showed up.
The two injured individuals were taken to nearby Corinth hospital, where they are reported to be in a non-life-threatening condition.
Police were searching for the perpetrators.