The stabbing to death of three young girls in the northwest English town of Southport last week has been seized on by anti-immigrant and anti-Muslim groups, with disinformation spread online contributing to disorder in towns and cities.
"Whatever the apparent motivation, this is not protest, it is pure violence and we will not tolerate attacks on mosques or our Muslim communities," Starmer said on Monday after an emergency meeting with police and prison chiefs.
"The full force of law will be visited on all those who are identified as having taken part."
Interior minister Yvette Cooper says rioters were trying to "to stir up racial hatred". (AP PHOTO)
The violence erupted last Tuesday after social media posts said the suspected attacker in Southport was a radical Islamist who had just arrived in the United Kingdom and was known to intelligence services.
Police say the 17-year-old suspect was born in the UK and they are not treating it as a terrorist incident.
Protests, mostly involving a few hundred people, have continued across the country, with bricks thrown at police officers, shops looted and mosques and Asian-owned businesses attacked.Â
Interior minister Yvette Cooper said rioters had felt "emboldened by this moment to stir up racial hatred".
She promised a reckoning to those involved, saying the government would back punishments ranging from jail sentences to travel bans.
Police have arrested 378 people since the start of the disorder, the UK's National Police Chiefs' Council said.
"Violent disorder is a serious offence which often comes with a lengthy jail term," NPCC Chair Gavin Stephens said.
In Rotherham, northern England, protesters on Sunday tried to break into a hotel that housed asylum seekers in what Starmer called an act of "far-right thuggery".
The killings of three young girls in the English town of Southport sparked sometimes violent demos. (AP PHOTO)
Elsewhere largely young men, some draped in the UK flag, hurled rocks and shouted "Stop the Boats," a reference to migrants arriving in dinghies on the south coast.
Many rioters were met by large groups of counter protesters, with police often struggling to keep the two sides apart.
Police in Liverpool said a 14-year-old boy was among those charged with violent disorder.
Starmer said a "standing army" of specialist police officers would tackle outbreaks of violence where needed.
Police have blamed online disinformation, amplified by high-profile figures for driving the violence.
Stephen Yaxley-Lennon, known by the pseudonym Tommy Robinson and previously the leader of the defunct anti-Islam English Defence League, has been blamed by media for spreading misinformation to his 875,000 followers on X.
"They are lying to you all," Yaxley-Lennon said.
"Attempting to turn the nation against me. I need you, you are my voice."
Interior minister Cooper told broadcasters that the government would pursue the spread of online disinformation with social media companies, and she did not accept that concerns about immigration could justify the violence.
"Reasonable people who have all those sorts of views and concerns do not pick up bricks and throw them at the police," she said.
