Manchester United and Manchester City fans brawled in the streets as tensions spilled over following Saturday's derby at Old Trafford.
The Blues came out on top on the pitch but ugly scenes after the game put a dampener on the first meeting between Jose Mourinho and Pep Guardiola in the Premier League.
Rival hooligans used roadside objects as well as their fists as they fought each other in the Northern Quarter area of Manchester before police arrived and the thugs dispersed.
Just two men initially squared up on Thomas Street, but soon more than a dozen were brawling.
Crates, rubbish, signs, chairs and a table were all sued as weapons, with several people seen filming the incident on their mobile phones.
Over 70,000 people were in attendance at the match, with police saying it passed 'largely without issue'.
However, five arrests were made, including two men for affray and another for ticket touting, who all remain in custody.
Two men were also arrested for breach of the peace and were released.
It is yet to be confirmed whether any of the arrests were connected to the ruckus in the Northern Quarter.
Chief Inspector Dean Howard, match commander, said: “There was a lot of excitement surrounding today's game and I want to thank the fans as well as local residents for their co-operation today.
In pictures: Manchester United 1-2 Manchester City
“This was the first derby of the season and although we have a lot of experience policing high profile football fixtures, your support does make all the difference.
“Apart from a handful of arrests, the vast majority of supporters were a credit to their teams and enjoyed the match in a safe environment for all.”
It was not the only instance of football violence in the Premier League this weekend, as West Ham fans fought among themselves at the London Stadium during their 4-2 defeat against Watford.
Problems arose when supporters' were standing - leading to confrontations with stewards who stepped in to ask them to sit down. Unsavoury footage posted on social media sites had been posted even before the final whistle blew.
West Ham have worked hard behind-the-scenes to attract a new generation of supporters to the former Olympic Stadium, offering season-tickets for £99 to youngsters.
There has only been one arrest so far this season but around one dozen supporters have had their season-tickets cancelled.
West Ham released the following statement: "West Ham United unreservedly condemn the behaviour of the individuals involved in incidents during today's fixture against Watford.
"While these isolated incidents were quickly brought under control, this behaviour has no place in football and West Ham United will work tirelessly to eradicate such incidents.
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"We are currently undertaking an immediate full review with all stakeholders.
"This includes police, stadium landlord and operator LS185, who are responsible for appointing and managing stewards and security, to ensure we eradicate such incidents moving forward.
"Our policy on this behaviour remains one of zero tolerance and we will work with the police and other stakeholders to identify the individuals involved.
"Once identified, they will be banned from attending any West Ham United fixture for life and we will request the courts serve banning orders to prevent these individuals attending any football."
On the pitch at Old Trafford, goals from Kevin De Bruyne and Kelechi Iheanacho secured derby day victory for City and Guardiola.
Zlatan Ibrahimovic responded for United after a howler from new Blues goalkeeper Claudio Bravo, but the visitors saw the second half out to register three points on enemy soil.