Olimpija Ljubljana and Borac Banja Luka fans clashed at the Stozice Stadium during their Conference League tie on Thursday night.
There were 84 minutes on the clock and the score 0-0 when a skirmish broke out in a stand behind one of the goals.
The two sets of fans were filmed hurling missiles at each other, with some carrying metal barriers to use as projectiles.
A small number of rival fans could also be seen trading punches.
The referee stopped the game while some Borac players tried to calm the fans down, but failed.
Local riot police were called in to restore order.
The game eventually ended in a 0-0 draw, giving Borac a 1-0 aggregate victory.
