The Manchester City team bus suffered a smashed window on the approach to Anfield as Liverpool fans ignored warnings over flares and smoke bombs ahead of their Champions League quarter-final.
The atmosphere had been vibrant with a number of people climbing up lampposts, walls and road signs to catch a glimpse of the teams as they arrived.
City arrived first but their bus became a target for a few missiles as it slowed to navigate the corner of Arkles Lane and Anfield Road, where most of the fans were gathered.
A Liverpool statement read: "The club condemns in the strongest possible terms the scenes which preceded our Champions League quarter-final, which resulted in damage being inflicted on the Manchester City team bus during their arrival at Anfield.
"We apologise unreservedly to Pep Guardiola, his players, staff and officials caught up in the incident.
"The behaviour of a number of individuals was completely unacceptable and the club will co-operate fully with the authorities to identify those responsible.
"The priority now is to establish the facts and offer Manchester City whatever support is necessary."
Liverpool went on to take a 3-0 advantage in the Champions League quarter-final tie.
Manchester City manager Pep Guardiola said in his post-match press conference: "Yesterday you explained that was going to happen and it happened.
"Normally when the police know it is going to happen they try to avoid it happening. I didn't expect that from Liverpool. We came here to play football.
"I don't understand these situations. The bus is destroyed. I didn't expect it from a club as prestigious as Liverpool. Hopefully it doesn't happen again."
Merseyside Police said: "Thankfully no-one on the bus was injured, but injuries were caused to two of our officers when projectiles were thrown towards the bus. The officers and stewards are there to protect the public and keep them safe.
"This behaviour by a number of people who threw bottles, cans and pyrotechnics towards the bus is completely unacceptable and we will conduct enquiries to identify who was responsible and bring them to justice."