A British Sikh man's conviction for the murder of a teenager triggered violent clashes targeted at the police in the UK, after body-worn camera footage showed officers handcuffing the man in his final moments over an allegation of racism.

Large crowds descended upon Southampton on Tuesday evening as officers from the Hampshire and Isle of Wight Constabulary lined up in riot protection gear near the home of Vickrum Digwa, sentenced to life imprisonment for stabbing 18-year-old Henry Nowak to death.

They were pelted with stones and bottles as the protesters heard from anti-immigration activists, who condemned so-called "two-tier policing" or prioritising one community over another.

The force's chief constable, Alexis Boon, said 11 officers and a police dog sustained injuries during the clashes, which sparked "fear and division" in the community.

"There can be no justification for hijacking this tragedy to stir up violence and disorder. Those responsible can expect to face the full force of the law," said UK Home Secretary Shabana Mahmood.

She echoed Prime Minister Keir Starmer's appeal from Downing Street to heed the Nowak family's powerful call to not allow the killing to "create further division, hatred or tension" and allow the Independent Office for Police Conduct (IOPC) investigation into the actions of the police officers at the scene of the crime to be completed.

There are concerns that the issue is being seized upon by far-right groups such as Reform UK and Restore Britain for electoral gains in a key by-election in Makerfield, northern England, later this month.

The trial has also brought scrutiny over the Sikh community's legal dispensation to carry the ceremonial dagger or kirpan, after Digwa used self-defence as an argument in court over the use of a 21-cm knife he carried for religious reasons.

Judge William Mousley noted in his sentencing remarks at Southampton Crown Court earlier this week that he belonged to an order of Sikhs called the Nihang, who have a tradition of having a second knife that is often fully visible.

"It is a religious and, consequently, legal requirement that a kirpan should only be used offensively as a last resort, which would include its use in legal self-defence," he stated.

After it emerged in court that Digwa had lied about being racially threatened during the incident last December, several British Sikh organisations and members of Parliament have spoken out in solidarity with the victim's family and against the unfair targeting of the kirpan.

"This case was about the murder of Henry Nowak by Vickrum Digwa. It is not about religion or racism. It was the criminal act of an individual who alone bears the responsibility for his actions," reads a joint statement by the British Sikhs All Party Parliamentary Group (APPG).

Chaired by Labour MP Jas Athwal, other signatories include Sikh heritage parliamentarians Satvir Kaur, Tanmanjeet Singh, Baggy Shankar, Jeevun Sandher, Sonia Kumar, Harpreet Kaur Uppal, Preet Kaur Gill, Warinder Juss, Kirith Entwistle and Gurinder Singh Josan, who wears a kirpan as a Nanaksari Sikh.

"The judge was clear that Digwa abused the responsibilities that accompany religious freedoms and that his actions stirred racial tension and caused fear within the Sikh community itself... At a time when emotions are understandably raw, we urge people not to allow the actions of one murderer to divide communities or fuel hostility towards innocent people," they said.

Many of them also participated in a debate in the House of Commons on Tuesday, during which Mahmood made a statement highlighting the legal protections in relation to the kirpan as one of the five holy items of the Sikh faith under the UK's Offensive Weapons Act of 2019.

The UK's National Police Chiefs' Council are reviewing an anti-racism commitment policing document in response to "legitimate concerns about how some of these commitments are worded or phrased".

The guidance, which was issued last year, suggested officers should treat ethnic minorities differently to ensure what it is termed as "equality of outcomes".

Digwa's mother, 53-year-old Kiran Kaur, remains in prison for her role in removing the murder weapon from the scene of the crime in Portswood, south-east England, in the early hours of December 4 last year and will be sentenced on July 17.

Meanwhile, his father, 52-year-old Moga Singh, and elder brother Gurpreet Digwa, 27, were released on bail after appearing before Southampton Magistrates' Court on Tuesday, faced with six counts of possessing offensive weapons, including an axe in a private place.

The offences relate to a search of the Digwa home on the day of Nowak's murder last year, with their legal proceedings adjourned for a hearing on July 9.