Ten police officers were injured when rival fans rioted in Athens before Panionios were due to meet Olympiakos in a game that was eventually postponed as a result of the violence.
Police said the clashes grew violent when more than 600 fans of visiting Olympiakos stormed the stadium, clashing with anti-riot police and fans of Panionios.
The decision to cancel the match came when hundreds of people holding sticks and throwing stones, encroached onto the pitch.
Therre was further violence outside the Olympic Stadium involving fans of Panathinaikos and AEK. Police said a fan and a passer-by were injured and two motorcycles when Panathinaikos supporters were hit with firebombs thrown by rival supporters.