Rangers midfielder Glen Kamara accused Slavia Prague defender Ondrej Kudela of "vile racist abuse" as the fall-out from Thursday night's Europa League clash continued to escalate.
Kamara issued a statement through his lawyer in which he gave a graphic account of the alleged incident – which Kudela denies – and demanded action from UEFA.
It came hours after Slavia asked police to investigate allegations that a Rangers player carried out an assault in the Ibrox tunnel – and claimed Gers boss Steven Gerrard is a key witness.
In the statement Kamara said: "If UEFA genuinely wants to 'show racism the red card', then it's time to stop the tokenism and take a zero-tolerance approach.
"As a player I do not expect myself, nor any other to have to tolerate racial hatred on or off the pitch in 2021.
"The vile racist abuse by Ondrej Kedel [sic] took place on the international stage, and any failure to act by UEFA will be viewed as a green light for racism."
Kamara had to be held back by team-mates as he reacted with fury when Kudela wandered alongside him late in the game, cupping his hand before allegedly whispering a discriminatory slur – "you're a f****** monkey, you know you are", according to the Finn's statement – into the midfielder's ear.
The match, which was won 2-0 by Slavia after Gers had two men sent off, was played to a finish as the Light Blues opted against walking off in protest.
Gerrard and Rangers chairman Douglas Park, however, were later seen confronting the Slavia delegation after the full-time whistle as they raged against the treatment of Finland international Kamara.
Slavia say a Rangers player landed a punch on Kudela as the altercation spilled over into the tunnel – a claim Rangers maintain has been made in order to deflect from the racism storm.
UEFA has already announced it will be investigating the game – but Slavia are also demanding that police officers probe events.
In a statement, the Czechs – who now will face Arsenal in the Europa League last eight – said: "Slavia Prague filed a criminal complaint with the Scottish Police through the Embassy of the Czech Republic in Great Britain for physically assaulting player Ondrej Kudela.
"The submission contains the names of witnesses who, in addition to representatives of Slavia Prague, were also representatives of the UEFA delegation and Rangers coach Steven Gerrard."
Rangers have opted not to respond to the latest development but managing director Stewart Robertson earlier released a statement insisting the newly crowned Scottish champions will object to any attempt to "deflect" away from the alleged racial abuse aimed at Kamara.
Gerrard has already warned UEFA it must not allow the claims to be "brushed under the carpet".
And Robertson has also turned up the heat on European football's governing body as he insisted "enough is enough".
He said in a statement: "The racist abuse suffered by Glen Kamara will not be tolerated by Rangers. As a club, we stand resolutely behind Glen as we support him and his team-mates.
"Several of our players have subsequently received racist, threatening and sickening abuse online. This is abhorrent and once again highlights the responsibility social media outlets have in eradicating abuse from faceless cowards.
"We refuse to acknowledge any attempt to defend, deflect or deny the abuse Glen Kamara experienced last night.
"This incident has been reported to the UEFA match delegate and we understand that it has formed part of his match report.
"UEFA will be well aware the football world is watching. We expect a robust and unequivocal response in relation to this incident. It cannot be merely 'swept under the carpet' – we are not prepared for Glen Kamara to be yet another statistic. Enough is enough."
UEFA initially said it was "aware of an incident which occurred in the tunnel after the end of the match" before later confirming it had now launched an investigation.
Slavia were quick to deny the allegations, issuing a late night statement which said Kudela had only called Kamara a "f****** guy".
But they launched into a stinging criticism of Rangers and their "unprecedentedly malicious play" and "brutal tackles".
Ondrej Kolar was left with a fractured skull and 10 stitches after Rangers striker Kemar Roofe planted his studs into the Slavia keeper's face in a high challenge, while Leon Balogun was also dismissed after collecting two bookings.
The Czech league leaders later issued another statement defending their player against Kamara's claims.
"Ondrej Kudela is one of the team captains elected in secret polls by the players who choose characters that enjoy their trust," it said. "He is a football gentleman and categorically denies and refutes any allegations of racism.
"We are shocked that his reputation and the club's reputation are being smeared without a single piece of evidence. The only 'alleged' evidence is the player covering his mouth – which Ondrej does on a regular basis when he talks to his team-mates during our games.
"Under the patronage and in the presence of the UEFA delegation, the coaches of both teams, Ondrej Kudela and Glen Kamara met. After the arrival of Slavia representatives, Ondrej was physically abused by the player of Rangers who then fled into the locker rooms followed by the manager Steven Gerrard without a single word of apology.
"We have felt a great respect to Rangers for their recent football performance and glorious history. However, we wish for a UEFA investigation into all incidents related to the recent match and will fully co-operate."
Police Scotland told the PA news agency on Friday evening that they have not heard anything from either club yet.