Police were forced to retreat during the protests over Henry Nowak's murder. Photo: Isabel Infantes/REUTERS

Demonstrators chanted "Henry, Henry" as they hurled stones, bricks, and chairs and clashed with police officers.

It comes after the highly publicised trial of Vickrum Digwa, a 23-year-old Sikh man who was found guilty of Nowak's murder last month.

Nowak was repeatedly stabbed by Digwa as he made his way home from a night out with friends in December. Digwa, who was sentenced to life in prison with a minimum term of 21 years on Monday, falsely told police who attended the scene that he had been the victim of a racist attack.

Officers initially handcuffed and arrested Nowak as he lay dying, with bodycam footage of the incident showing Nowak telling police that he'd been stabbed and that he "can't breathe".

Reform party leader Nigel Farage commended Nowak's family for their "extraordinarily dignified" response to his killing but called for others to respond with "pure cold rage".

"The biggest fear a police officer now has going about his or her duty on the street is the fear of being reported for having acted in a way that was racially biased," Farage said in a clip posted to social media.

British Prime Minister Keir Starmer has criticised Farage's comments, saying he was attempting to "create division" against the wishes of Nowak's family.

In a post on X, Home Secretary Shabana Mahmood wrote that Tuesday's violence was "completely unacceptable," adding that "there can be no justification for hijacking this tragedy to stir up violence and disorder".

Sikh community groups have condemned Nowak's killing as a "moment of madness by an individual for which there can be no excuses".

But they said the wider Sikh community had "unacceptably faced considerable abuse and hate during the trial as many do not understand the law, the significance of the Kirpan or the responsibility associated with wearing a Kirpan".

A Kirpan is a small blade Sikhs wear as part of their religious uniform. Prosecutors say Digwa carried a standard Kirpan as well as a large dagger.

"We understand in this case the weapon that may have been used was not the normal Kirpan worn by fully practicing Sikhs," the Sikh community's joint statement said. "This nuance is critically important and may not have been explained or understood by those asked to give evidence in this case".