Police officers faced “serious and sustained levels of violence” after disorder broke out in Sunderland on Friday night.
Northumbria Police said three of its officers were injured during the unrest and needed hospital treatment.
Eight people have been arrested after a police premises was ransacked and an adjacent building was set alight.
Beer cans and bricks were thrown at riot police outside a mosque and at least one car was set on fire during the disorder.
It is the latest episode of unrest to break out in towns and cities across England following the killing of three young girls in Southport on Monday.
Northumbria Police Ch Supt Helena Barron said officers had been met with “serious and sustained” levels of violence, which was “utterly deplorable”.
She said a full investigation was under way to identify those responsible for any criminal behaviour.
“I want to make it absolutely clear that the disorder, violence and damage which has occurred will not be tolerated,” Ch Supt Barron added.
Of the three injured police officers, one has been discharged and two remain in hospital for further treatment, she said.
Some members of the crowd could be heard shouting Islamophobic slurs and chanting in support of far-right activist Stephen Yaxley-Lennon – who uses the alias Tommy Robinson.
Mr Yaxley-Lennon’s X account has promoted false claims that the alleged Southport attacker had been an asylum seeker who recently arrived in the UK by boat.
Mounted police were deployed to Sunderland’s city centre to push back demonstrators, some of whom were in masks.
Officers also had beer barrels thrown at them, as young men shouted: “Whose streets? Our streets”.
Home Secretary Yvette Cooper said criminals attacking the police would “pay the price for their violence and thuggery”.
<<BBC>>
