MAYHEM broke out after Arsenal's win over PSV at the Emirates as away fans ripped out seats and chucked flares at the home support.
Mikel Arteta's men edged past the Dutch outfit thanks to Granit Xhaka's second half goal - a result which sees them qualify through the Europa League group stage.
And the travelling PSV contingent of around 3,000 did not take the result well as a flare was launched at the Arsenal fans just minutes after the final whistle.
Those in the away end could then be seen forcibly removing the seats and chucking them.
Riot police intervened to separate the two sets of supporters and diffuse the situation.
Uefa are set to investigate and could hit PSV with a fine after what was an ugly end to another positive night for the North London outfit.
READ MORE ON ARSENAL
Arteta's men clinched an eighth successive win in all competitions as they eventually broke down a stubborn PSV outfit.
Gabriel Jesus went close on a couple of occasions in the first half, but the hosts were ultimately left frustrated.
In the second period the Premier League leaders ramped things up as Jesus, Bukayo Saka and Eddie Nketiah narrowly missed opportunities to clinch the opening goal.
But it eventually came 20 minutes from time as Takehiro Tomiyasu's cross picked out Xhaka and the Swiss midfielder found the far corner with his effort.
Most read in Football
HOW TO GET FREE BETS ON FOOTBALL
Speaking after the game, match-winner Xhaka said: "We had chance after chance and we didn't have the luck to score earlier but we had the passion to keep the ball, keep creating the chances and I think we deserved the win.
"In the first half we did a lot of pressure. Everyone who comes here is playing similar to PSV, we knew they had the quality to kill us on the counter attack but we did amazing.
"I'm so happy to score. I don't know when I scored for the last time with the right foot but so happy. It doesn't matter which foot, or who scores.
"It gives us confidence and on to the next one. When you win games you have to be happy. Everything is going well at the moment but for us it is not a surprise, we're doing a lot of work.
"We win and lose as a team and at the moment we are very dangerous. We wanted to go through and are very happy."