More than 100 people, most of them Croatian nationals, have been detained since August pending trial over the violence before a UEFA Champions League match between AEK Athens and Dinamo Zagreb that led to AEK fan Michalis Katsouris being stabbed to death. More than 80 of them are still detained in Athens.

Greece has tried for years to reform soccer, which has been plagued by violence on and off the pitch.

In another incident on Thursday night, the police detained about 400 fans after a police officer was critically injured in clashes that broke out during a volleyball match in Athens between local teams Olympiacos and Panathinaikos at Olympiacos' Rentis stadium.

The officer remains in hospital in a critical condition, an Athens police official said on Friday.