Due to the unrest among the Danish fans after the game, the organizers chose to empty the stands with the traveling spectators before the Víkingur fans were let out.
Nevertheless, a riot broke out between Brondby supporters and the police, who used pepper spray to stop the situation from escalating any further.
According to the media outlet Visir, two of Brondby's own security guards were pepper sprayed in the eyes during the riot, which is why both had to be treated in an ambulance.
According to TV2 Sport, witnesses also say that an Icelandic police officer was punched in the face.
According to Víkingur's CEO, Brondby fans caused damage to the stadium – including broken toilet trolleys and equipment, which amounts to around €34.000.
But the trouble did not stop at the stadium.
Later in the evening, a number of Brondby fans allegedly went to a bar where Vikingur supporters were staying, and the fight broke out again.
"They all came wearing masks and attacked us. It ended in a bloody fight. Fortunately, no one ended up in the emergency room, but they were clearly bitter about the defeat", an Icelandic fan tells Visir.
For that reason, the Danish fans were allegedly blacklisted from the bar.
In addition, some Brondby fans allegedly smashed a framed FC Copenhagen shirt that was hanging on a wall in the bar before the match.
Brondby lost the match 3-0 and faces a tricky return leg if they are to proceed to the playoff round in the tournament against French outfit Strasbourg.