Merseyside Police have launched an investigation after Real Madrid's team bus was targeted outside Anfield on Wednesday night prior to their Champions League quarter-final second-leg tie against Liverpool.
When one of Real's buses parked up at the Kop end of the ground after the team had disembarked, it was apparent the outer pane of a double-glazed window had been smashed.
Liverpool staff were seen cleaning up a pile of broken glass on the ground with Merseyside Police officers in attendance.
Stewards could be seen ushering away supporters, who had gathered outside the ground, from near the bus as the clean-up operation got underway.
Hundreds of fans lined Anfield Road, very few wearing masks or observing social distancing, to greet both teams as they arrived.
Merseyside Police have launched an investigation into the incident and the force has confirmed that no individuals were injured as "a number of items" were thrown at the vehicle.
Chief Superintendent Zoe Thornton said: "We can confirm an investigation is underway after damage was caused to the Real Madrid team bus this evening, as it approached Anfield Stadium ahead of Liverpool's Champions League match with Real Madrid.
"Despite the advice to avoid attending the ground, approximately 400 people attended Anfield Road and as coaches approached, a number of items were thrown at the Real Madrid team bus. We are aware of images which show the outer pane of the lead coach window being damaged, the glass did not break through and there are no reported injuries.
"A number of pyrotechnics were also lit in the area, which significantly reduced visibility and could have put other people in danger.
"As with all matches, we have worked very closely with both clubs to ensure the safety of the public and the teams themselves, and the disgraceful behaviour of those involved this evening is extremely disappointing and totally unacceptable. Such incidents will not be tolerated under any circumstances.
"A dedicated investigation team will be reviewing CCTV footage from the area, along with our own body worn camera footage, and working closely with the club to identify those responsible. I would also ask anyone who was in the area and captured mobile phone video footage of the incident to please get in touch."
A Liverpool spokesperson said: "We condemn unequivocally the actions that led to Real Madrid's team bus being damaged during its arrival to Anfield this evening.
"It is totally unacceptable and shameful behaviour of a few individuals. We sincerely apologise to our visitors for any distress caused.
"We will work together with Merseyside Police to establish the facts and identify those responsible."
The Reds are 3-1 down in the tie, which is to be played behind closed doors, with two goals from Vinicius Junior and one from Marco Asensio in the first-leg giving Real the advantage on aggregate ahead of the game.