Eleven people were arrested after ugly scenes during Sunday's Athens derby between Olympiakos and Panathinaikos, Greek police announced Monday.
"A total of 26 persons were brought in to police headquarters of which 11 were detained for violent acts before, during and after the match at the Karaiskakis Stadium," a police statement said.
Police said they used "a limited amount of chemicals" in order to contain the unruly Olympiakos fans.
Panathinaikos coach Giannis Anastasiou was slightly injured when he was struck in the face by a full plastic cup of soda thrown at him in the second half of the match.
In another incident, a flare thrown on the pitch narrowly missed hitting several players.
Olympiakos' Nigerian forward Michael Olaitan collapsed in the first half and was taken to hospital where he was diagnosed with a heart complaint caused by anxiety and stress.
Doctors kept him in the hospital for further tests on Monday.
Panathinaikos surprised league-leading Olympiakos 3-0 but the losers still hold a 19-point lead in the standings.