Olimpija and Maribor fans clashed at Ljubljana’s Stozice Stadium before their derby match on Saturday.
About 15 minutes before kick-off, around 20-30 Olimpija fans invaded the pitch and ran towards the away end to confront their Maribor rivals.
Punches and seats were thrown between the two sets of fans with riot police called in to separate the sides.
The pitch invasion came after Maribor fans had taken an Olimpija flag from a nearby stand.
The flag was then burned in the away end.