Eight people have been arrested and three police officers taken to hospital following rioting in Sunderland city centre, police said.
It comes after rioters battled police following a planned protest linked to the Southport knife attack.
Northumbria Police Chief Superintendent Helena Barron said in a statement: “We can confirm that three officers were taken to hospital for treatment of injuries.
“One has since been discharged with the other two remaining in hospital for further treatment.
“We also thank our partners for the significant support they have shown throughout the evening.
“Anyone involved in the disorder we have seen can expect to be dealt with robustly – and that action has already begun.”
Hundreds of people gathered in Keel Square, many of them draped in England flags, on Friday evening.
Members of the crowd chanted in support of Tommy Robinson, while others shouted insults about Islam.
Mounted police followed the march, along with officers in vans who battled their way through traffic to keep up.
However, some protesters descended into violence, setting an overturned car on fire, while others targeted a mosque.
Videos posted on social media appeared to show a fire at a city centre police office, which was marked permanently closed on Google Maps and was no longer listed on a police station finder on Northumbria Police’s website.
Police in protective gear came under sustained attack as rioters set off fire extinguishers on them on High West Street.
There was also a standoff between police and protesters outside a mosque on Sunderland’s St Mark’s Road.
Police in riot gear came under attack with stones and beer cans thrown.
Some protesters argued about “two-tier policing” as the police threw a protective ring around the mosque.
Mounted police pushed back demonstrators, some of whom were in masks.
Meanwhile, customers in the next-door Aldi filmed the scenes on their phones through the shop window.
Ms Barron condemned the scenes of violence as “completely unacceptable”.
She said: “I want to make it absolutely clear that the disorder, violence and damage which has occurred will not be tolerated.
“The safety of the public is our utmost priority and when we became aware that a protest had been planned, we ensured there was an increased policing presence in the city.
“During the course of the evening, those officers were met with serious and sustained levels of violence, which is utterly deplorable.
“In the face of these attacks, they showed unwavering commitment for which I wholeheartedly thank them, as I am certain the overwhelming majority of people in Sunderland will also.”
She continued: “The right to lawful protest is a key part of any democracy, which the police uphold. However, we will not accept people using them as a means to commit crime.
“We want to be clear anyone planning to involve themselves in disorder in the future should stay at home.
“We also know the behaviour displayed is in no way representative of our friendly and welcoming region.
“We therefore want to deliver a further message direct to our communities – we are aware that the actions we have seen this evening can be an attempt to drive division amongst us all and we are committed to making sure that does not happen.
“We have incredibly cohesive communities here which we are proud to be a part of and to serve.
“This is just one of the reasons which makes our region such a special place to live, work and visit. We are stronger together.”
Sunderland Central MP Lewis Atkinson said he was appalled by the violent scenes, which he described as “criminal thuggery”.
In a post on X, he said: “I am appalled by the disorder in the centre of Sunderland tonight.
“Our city is not represented by a tiny minority causing trouble.
“Northumbria Police have my full support as they respond to criminal thuggery and work to protect all the communities of our city.
“Tomorrow the people of Sunderland will come together and continue to build the bright future that we have – a future where every community of our city feels safe and prospers.”
Home Secretary Yvette Cooper said those stoking the scenes of disorder “do not represent Britain”.
She posted on X: “Criminals attacking the police & stoking disorder on our streets will pay the price for their violence & thuggery.
“The police have the full backing of Government to take the strongest possible action & ensure they face the full force of the law.”
Sunderland AFC said the city “will forever be for all”.
“Tonight’s shameful scenes do not represent our culture, our history, or our people,” a post by the team’s X account said.
“Our great city is built on togetherness and acceptance, and Sunderland will forever be for all. We are stronger as one community. Now. Then. Always.”
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