(West Midlands), Dec 1 (BBC) - Thirty-nine people have been arrested after violence broke out in the build-up to Aston Villa's game with Legia Warsaw in Birmingham on Thursday night.
Four police officers were hurt in clashes with away fans near Villa Park.
West Midlands Police said officers were "faced with disgusting and highly dangerous scenes", including having flares thrown at them.
The Europa Conference League tie went ahead with away fans blocked from entering the stadium over safety fears.
Officers with batons and shields were seen trying to regain control of the area while missiles were launched at them as fans of the Polish side attempted to force their way through barriers.
Several videos posted on social media showed the disorder, including missiles being thrown at fans in the ground from a road adjacent to a stand.
West Midlands Police said one of the injured officers had been taken to hospital, and said two police horses and two police dogs had also been hurt.
Disorder is believed to have been triggered by tensions over restrictions on the number of away fans who were going to be permitted to enter Villa Park for the match.
Police said the allocation for visiting supporters had been reduced to 1,000 tickets on the advice of local emergency services, adding Legia fans had "been involved in previous match day disorder".
In a statement posted on the club website ahead of the game, the Polish side accused Aston Villa of restricting access to their fans despite assurances, calling the move "counterproductive and baseless".
It said the club's owner and other senior executives who were due to be at the game were boycotting it in response to the move.
In a statement released after the match, Chief Inspector Tim Robinson said: "This should have been a great evening of football which was enjoyed by fans from both clubs.
"Unfortunately, there were appalling scenes which saw away fans dangerously throw flares and other missiles at our officers."
He said "due to the extreme violence" police were left with "no other choice but to prevent away fans entering the stadium. The safety of everyone is our priority, and clearly we had no other option."
Aston Villa said in a statement: "In spite of numerous requests for cooperation from Legia Warsaw concerning their travelling supporters, especially in the last two days, no assistance on the serious safety matter of away fans attending Villa Park was forthcoming from the visiting club.
"The club has repeatedly, including this morning, raised concerns in conjunction with Uefa and all the relevant authorities to Legia that ticketless away supporters were attempting to attend Villa Park."
West Midlands mayor Andy Street urged Uefa - European football's governing body - to "swiftly... take strong action" against Legia Warsaw.
Dutch police officers were injured during large-scale disorder during their match against AZ Alkmaar last month.
Aston Villa won the game 2-1 courtesy of a 58th minute goal by Alex Moreno.