The Metropolitan Police said it is investigating six stabbings that took place after the Arsenal Champions Parade in London.
The force said a total of 24 people were arrested after more than 500 officers were deployed across the event on Sunday, alongside specialist search and drone teams.
Officers thanked the vast majority of people for “celebrating responsibly”, but said investigations continue.
Up to a million Arsenal fans were estimated to have lined the route surrounding the Emirates Stadium in Islington for the parade, which marked the north London club winning the Premier League for the first time in 22 years.
The arrests included 10 people on suspicion of assaulting police, with one officer suffering a slash wound to the hand and another hit on the head by thrown objects.
Three people were arrested on suspicion of sexual assault, and one person was arrested on suspicion of grievous bodily harm. Everyone arrested was taken into custody.
Damage was also caused to four police vans in Islington, causing broken lights and dents, but no arrests have been made.
The Met said it dealt with six stabbings “on the parade footprint” after most of the crowds had dispersed in the evening.
Most of the victims were not seriously injured, but one man in his twenties was taken to hospital in a life-threatening condition at around 8.30pm. He is now in a stable condition.
A Section 60 order was authorised overnight in the area to help prevent further offences and give officers additional stop and search powers.
The London Fire Brigade also confirmed its crews had rescued around 75 individuals from various elevated positions throughout the event, urging fans to avoid climbing onto rooftops.
Commander Stuart Bell, who led the Met’s public order operation over the weekend, said: “I would like to thank the vast majority of the hundreds of thousands of Arsenal supporters who attended the day to celebrate safely and responsibly.
“There was a police presence along the route throughout the event, supporting event organisers and stewarding operations.
“However, we had been clear that violence and other criminality would not be tolerated and, unfortunately, there were pockets of anti-social behaviour and incidents where officers needed to intervene, including assaults on their colleagues.
“As the evening progressed and the majority of the crowds made their way home, there was sadly further violence, including gang-related incidents.
“Officers were swiftly on scene to each stabbing and investigations are ongoing.”
Chief Superintendent Jason Stewart, who leads policing in Islington, added: “This, of course, was a huge and significant event for our community and Arsenal fans more widely, and we worked closely with the local authority and other partners to plan for the event and then throughout the day.
“Our officers are back out on patrol today to provide visible reassurance, and our investigation teams are working hard to identify offenders and bring them to justice. We stand with our local communities against violence.”
