Uefa has opened a formal investigation after being handed TV footage appearing to show black fans being attacked during Dynamo Kiev's Champions League draw against Chelsea last week.
European football's governing body will assess charges of racist behaviour, crowd disturbances and stairways being blocked among the Kiev fans.
The footage was passed to Uefa by European anti-discrimination body Fare.
It shows four men being attacked by Kiev fans and then trying to flee.
They then appear to be set upon by other fans as they try to leave the Ukrainian club's Olimpiyskyi Stadium.
Last season, Dynamo were fined and ordered to close part of their stadium on two occasions as punishment for racist behaviour in the crowd at Europa League matches.
The latest incident caused further controversy when Volodimir Spilchenko, the director of the stadium said in an interview with a TV journalist that he was willing consider the segregation of black fans.
But a statement was later released to say the comments had been taken out of context.
Fare executive director Piara Powar said: "It's quite clear the attack took place. It's documented in video and subsequently other videos and still photographs have come to light.
"From what we've now seen it was a racist attack that was accompanied by people talking about 'white power'."