London - Police on Monday condemned violent clashes between Millwall and Everton fans at their weekend FA Cup clash as "some of the most shocking football violence we have seen for some time".
An Everton supporter suffered a "life-changing injury" after an attack from a Millwall fan during ugly scenes in south London before kick-off on Saturday.
The injured man named himself on social media as Jay Burns, posting an image showing a long scar down the right side of his face, while a police officer was also injured.
The Metropolitan Police are also investigating allegations of racist chanting during the match, some of which was captured on video and posted on social media.
"The disorder which occurred before, during and after the Millwall v Everton Cup match on Saturday, 26 January was some of the most shocking football violence we have seen for some time," said deputy assistant commissioner Matt Twist.
"The abhorrent behaviour lasted a number of hours, involved dozens of people, and resulted in at least one serious injury.
"One man was taken to hospital with a horrific, life-changing injury to his face. One of our officers was also injured, and has now been discharged from hospital."
The Football Association has said it is investigating while Millwall have pledged to hand out life bans to anyone found guilty.
Millwall chief executive Steve Kavanagh said the incidents had marred the 3-2 win for the Championship side against their Premier League opponents, but believes the blame cannot be pinned solely on the football club.
"Millwall Football Club cannot be responsible for educating the whole of south east London and this group of people," he told BBC Radio.
"We need to all come together and find a way of trying to get this education," he added. "Football is fantastic, let's use its place in society to educate people and find a way of doing that and really coming together."