Liverpool are investigating claims fans were mistreated by Spanish police, with some allegedly assaulted and denied entry to the stadium before Tuesday’s Champions League draw with Sevilla.

The match kicked off with almost half the away section empty. Supporters were reportedly turned away or told to sit in seats they had not been allocated. There were also claims on social media, which have not been verified, of fans being attacked by police.

“Following detailed and troubling accounts given by Liverpool supporters attending the match, the club is seeking to establish the facts regarding their treatment at the hands of the host stewards and local police force,” a Liverpool spokesman said. “The safety and security of our supporters is our paramount concern and we intend to gather all the relevant information before responding further.”

Jay McKenna, the chairman of the Liverpool supporters’ group Spirit of Shankly, said his organisation had received dozens of complaints from fans with more expected once people have returned home.

“A few dozen people have already been in touch in the immediate aftermath and a couple more today but most people are still travelling back,” he said. “We know the club are investigating and we are in touch with supporters, trying to get their experiences. We will then relay them to the club and Uefa. What we are hearing are a combination of things, of crowd control problems inside and outside of the ground.

“We’ve had supporters forced into various parts of the ground. There were fans who had tickets for the upper and lower tiers ending up next to each other, leading to more people in the upper tier than there should have been. One of our committee members has also reported being pushed and kicked from behind by a steward.”

Fans of Leicester City reported maltreatment at the hands of Seville’s police before their Champions League tie in the city in February and it is understood that complaints against Spanish police are a constant theme from travelling fans, not just from England but Germany and the Netherlands too.

The chief executive of the Football Supporters’ Federation, Kevin Miles, called for more to be done to protect supporters’ safety. “Sadly there was a predictable inevitability to these events as the Spanish police have a consistent track record of ill treatment and abuse of visiting fans,” he said.

“They particularly seem to relish attacking fans of English clubs. Through the network of Football Supporters’ Europe we have raised this matter repeatedly with Uefa and we know they share many of our concerns.”

Liverpool collapsed in the second half to squander a three-goal lead against Sevilla but a draw with Spartak Moscow at Anfield on 6 December will be enough to send them through to the Champions League knockout stages.