Protesters attacked police and started fires in the northeast English city of Sunderland on Friday as violence spread to another northern city following Monday's killing of three children in Southport.

Anti-immigrant demonstrators threw stones at police in riot gear near a mosque in the city before overturning vehicles, setting a car alight and starting a fire next to a police office, the BBC said.

Northumbria Police Chief Superintendent Helena Barron said in a statement, "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."

Three police officers were taken to hospital for treatment, and eight people have so far been arrested for offenses such as violent disorder and burglary, Barron added.

The demonstration in Sunderland was one of more than a dozen planned by anti-immigration protesters across the UK this weekend, including in the vicinity of at least two mosques in Liverpool, the closest city to where the children were killed.

Several anti-racism counter-protests were also planned.

British police were out in force on Friday across the country and mosques were tightening security, officials said.

A 17-year-old boy has been charged with the murder of the girls in a knife attack at a Taylor Swift-themed dance workshop in the northwestern seaside town of Southport, a crime that has shocked the nation.

Violent incidents erupted in the following days in Southport, the northeastern town of Hartlepool, and London in reaction to false information on social media claiming the suspect in the stabbings was a radical Islamist migrant.

In an attempt to quash the misinformation, police have emphasized that the suspect, Axel Rudakubana, was born in Britain.