Liverpool have condemned and apologised for the smashing of a window in a Real Madrid team coach prior to their Champions League match at Anfield, while Merseyside Police have launched an investigation into the incident.
A club spokesman said the behaviour "of a few individuals" was "totally unacceptable and shameful".
Hundreds of fans lined Anfield Road, very few wearing masks or observing social distancing, to greet both teams as they arrived for the Champions League quarter-final second leg with a number setting off flares and smoke cannisters.
It is not the first time the opposition coach has been damaged in the build-up to a match at Anfield.
Three years ago Manchester City's bus was hit by bottles and flares, ahead of another Champions League last-eight clash.
It caused so much damage City had to call for a back-up bus to take the players home after their 3-0 defeat that night.
On that occasion UEFA fined the club 20,000 euros (£17,000) for the damage as well as 6,000 euros (£5,200) for setting off fireworks and throwing objects.
