One man was stabbed in the face during what police believe to have been a violent clash on Saturday between opposing soccer fans ahead of Everton and Millwall's FA Cup match in London.

Local police say they believe fans of Millwall and Everton were involved in fighting before the match, during which a man was slashed in the face. He was taken to the hospital to be treated for his injuries.

Footage posted on social media shows two groups clashing outside of the Surrey Quays station, The Sun reports. Dozens of people are seen brawling and punching each other, as police desperately try to break up the melee.

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At one stage, a man is seen falling to the ground clutching his face. Images were later shared on social media allegedly showing the wounds suffered by the man who was slashed with a knife.

"The behavior of those involved in this incident is nothing short of disgraceful," said Detective Inspector Darren Young of the Metropolitan Police, adding that footage of the brawling which was circulating on social media has "quite rightly elicited shock and disgust."

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Everton fans were held back inside Millwall's stadium after the final whistle on safety grounds.

Millwall was renowned for its struggle with hooliganism in the 1970s and 80s. That reputation was revived during the FA Cup semifinals in 2013, when its fans turned on each other during a loss to Wigan at Wembley Stadium, leading to 14 arrests inside the stadium.

On the pitch on Saturday, Millwall upset their English Premier League opponent 3-2 to advance to the next round of the prestigious tournament.

The Associated Press contributed to this report.