Riot police with batons were deployed against Aberdeen fans as fighting broke out after the side's Europa League match in Cyprus.
The match itself was interrupted when supporters of Apollon Limassol threw flares onto the pitch.
More trouble erupted after the Dons' 2-0 defeat, as a small number of fans at the Aberdeen end clashed with stewards at the AEK Arena in Larnaca.
Police with batons and riot shields then moved in.
BBC Scotland's Scott Davie described "ugly scenes" between fans and stewards, and Aberdeen manager Derek McInnes said he heard supporters had been "treated terribly".
The BBC understands a small group of fans within the near 700-strong travelling support appeared to instigate trouble, which was restricted to inside the ground. There were no arrests and no reports of serious injury.
Fans have raised concerns about stewarding at the match, and the fact riot police appeared to use pepper spray when there were children and families nearby.
BBC Scotland understands that supporters have been sending video footage of the trouble to the club unsolicited, with Aberdeen officials determined to root out any troublemakers.
Derek McInnes later criticised stewarding at the match and said fans had been treated badly.
He told BBC Radio Scotland: "We expected it to be a bit volatile. We expected there to be plenty of passions from the side but it did boil over at times.
"I'm hearing our fans were treated terribly by the stewards here as well. Steaming in with flares and tear gas and everything else to try to defuse the situation.
"I didn't get to see it but I'm hearing it second-hand. And when you see some of the stuff that was going on.
"Things getting thrown onto the pitch, people spitting into the dugout, players getting thrown on.
"That's when you should have seen the stewards being more visible, not treating our fans the way they did."
The flare incidents took place early in the second half, with one landing inside the goal behind Dons goalkeeper Joe Lewis.
Television footage caught Swiss referee Stephan Klossner tell an official that he would abandon the match if behaviour did not improve, but it calmed down.
In a statement, Aberdeen FC said it had "commenced dialogue with the stadium operators, Apollon Limassol and the authorities" about the events.
It added: "As part of this, the club has requested that CCTV footage is interrogated in order to assist matters.
"The club will not be making any further comment until the conclusion of this comprehensive investigation."