Rangers manager Steven Gerrard said midfielder Glen Kamara told him he had been racially abused by Slavia Prague defender Ondrej Kudela in Thursday's Europa League last-16 match, a claim Gerrard backed with "100 percent" confidence given the trust he has in his player.
A scuffle broke out between sides in the final five minutes after Kudela appeared to whisper something in Kamara's ear.
The tie had already been effectively decided by that point, with Rangers down to nine men and down 3-1 on aggregate.