Bottles were thrown at police officers while they were treating a man who had been stabbed at an illegal street party.
Three officers were injured during the incident as they responded to the gathering in Basford, Nottingham at around 10pm on Saturday.
One officer was bitten after hundreds of people swarmed the streets with some seen defecating in public, according to witnesses.
The 18-year-old stabbing victim was taken to hospital with serious injuries that are not thought to be life-threatening.
Police said several people have been arrested and they are treating the stabbing as attempted murder
The party had been advertised on social media by a group of people suspected to be living in Bramble Close.
Officers responded to shut down the event earlier in the day when people started arriving and restricted access to the road to prevent more guests from attending.
Nottinghamshire Police said the gathering was brought under control at first but more people began to arrive, resorting to breaking through nearby gardens to get to the party.
Meanwhile, another group gathered nearby in David Lane and Mill Lane outside the police cordon.
As police tried to disperse the crowd, an 18-year-old man was stabbed several times.
Police were giving him first aid when members of the crowd began to throw bottles at them.
Three officers were left with minor injuries including one being bitten, Nottinghamshire Police said.
The force said they believe people travelled from outside Nottingham to attend the illegal meeting.
City Area Commander Superintendent Mat Healey said: “This was a brutal stabbing of a young man in the midst of a mob of people.
“We know there are several witnesses who will have seen what happened and we urge them to come forward now so we can bring those to justice who are responsible. There is no justification for this appalling attack.
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“Those who attended yesterday’s gathering did so knowing they were breaking the law and we know people came from outside of Nottinghamshire, which makes it even worse.
“This was irresponsible and that irresponsibility has led to the serious injuries that have been inflicted on the victim.”
Healey also said the attack on officers while they gave first aid to the victim was “just appalling”.
“This is not acceptable on any level by any right-thinking member of society,” he added.
“This was a dangerous situation for local people, and indeed for those that attended, but it was also extremely challenging and complex to police.”
The force said a man, 21, was arrested on suspicion of possession of a knife.
Several more people were arrested, including a 22-year-old man who was found with two knives in his possession.
He was also detained on suspicion of assaulting the officer arresting him.
People living nearby said the party was going on for at least seven hours, according to the BBC.
One woman living nearby told the broadcaster she first heard the party at about 3pm.
"It became quickly clear people were arriving by car travelling into the area, parking in surrounding streets, [and we] felt literally hundreds of people swarming around our streets," she said.
"People getting to the party were jumping over a large fence at the bottom of the cul-de-sac. People were drinking in the street and it was still going on at 9pm. We saw people defecating in the street."
"We are a community that needs answers today as to why people thought it was Ok to drive into our community, create anti-social behaviour and why was it not de-escalated," she said.
Anyone with any information or witnesses are urged to contact Nottinghamshire Police on 101 quoting incident number 304 on 12 June 2021.
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