By Alexander Smith

After three young girls were fatally stabbed at a Taylor Swift-themed dance event, a torrent of false claims from an online ecosystem of far-right extremists spread across the social media platform X, coinciding with a night of racist street violence spreading fear in an already-grieving English town.

A large group of far-right, mostly white men threw bottles and bricks at police officers and a mosque in the northwest town of Southport on Tuesday night. Twenty officers were injured and a police van was torched as the crowd chanted racist slogans against immigrants and Islam.

It is an unedifying pivot in a country that had been largely united in disbelief and sadness by the events of the day before. Rather than respectful mourning, the narrative was now centered on the hijacking of a vigil by extremists promoting a lie — that the attacker was an asylum-seeker, Muslim or both. It also risked puncturing the sense that Britain, which just weeks ago delivered the moderate center-left government of Prime Minister Keir Starmer in a colossal parliamentary landslide, had managed to evade the hard right and anti-immigrant turn taken by some countries on the continent.

Police arrested a 17-year-old on suspicion of murder and attempted murder. The suspect was born in the Welsh capital of Cardiff and had lived for years in a village near Southport itself, police said.

But there was much police did not say, owing partly to the suspect’s age, as well as strict media rules in Britain around arrests and prosecutions. Into this vacuum stepped a thriving trade of willful falsehoods — some of it from anonymous influencers but much of it from well-known public figures.

Online personalities such as internet influencer Andrew Tate and the British former boxer Anthony Fowler asserted that the person was an illegal immigrant or from Syria.

'Enough is Enough' protest in London

And newly elected British lawmaker Nigel Farage — an ally of former President Donald Trump — was also accused of emboldening those voices by asking whether police were withholding the truth about the killings from the public.

“I don’t know, but I think that’s a fair and legitimate question,” he said in a video message. “What I do know is that something is going horribly wrong in our once beautiful country.”

Farage, a well-known right-wing personality who is the head of Reform UK, a new party that won five seats in Parliament largely on an anti-immigrant platform, was condemned by a former senior police officer who was in charge of counterterrorism.

Neil Basu told The Guardian that Farage was emboldening the English Defense League, which was once a potent far-right organization but today is more a decentralized network of supporters and values.

“Nigel Farage is giving the EDL succor, undermining the police, creating conspiracy theories, and giving a false basis for the attacks on the police,” Basu told the newspaper.

“Has Nigel Farage condemned the violence? Has he condemned the EDL? Fomenting discord in society is what these people seem to exist for,” he added.

Disinformation and misinformation about Tuesday’s attack spread quickly on X and fueled the violence, said disinformation expert Marc Owen Jones, an adjunct professor at Northwestern University in Qatar. There were 27 million impressions “for posts stating or speculating that the attacker was Muslim, a migrant, refugee or foreigner,” he said.

“There is a clear attempt to exploit the tragic incident by right wing influencers and grifters, pushing an anti-immigrant and xenophobic agenda despite there being no evidence,” Jones wrote in a thread on X explaining his snap research.

The Liverpool Region Mosque Network also sought to contradict the online rumor mill.

Police faced violent demonstrators in the town of Hartlepool in northeast England, as far-right groups seek to stir anger over an attack they have sought to link — without evidence — to immigrants.

“A minority of people are attempting to portray that this inhumane act is somehow related to the Muslim community,” it said on X. “Frankly it is not, and we must not let those who seek to divide us and spread hatred use this as an opportunity.”

Tuesday night should have been focused on a peaceful vigil for the three girls who died, Alice Dasilva Aguiar, 9, Elsie Dot Stancombe, 7, and Bebe King, 6, and for the 10 other people injured, including two adults who were badly wounded in their apparent attempts to protect the kids.

Instead, the spotlight has inevitably been drawn by the violence just around the corner. There did not seem to be much mourning here; some of the rioters were laughing and seemed to be enjoying the excuse to clash with authorities. Another group brought a big box of alcoholic cider.

The violence injured 22 officers — eight with serious wounds — and three police dogs.

Britain has, in the main, become less racist after a long history of colonialism, according to Sunder Katwala, director of the think tank British Future, which focuses on immigration, identity and integration. But police in Britain say they have become increasingly worried in recent years about an increase in online extremism.

That covers militant antivaccine campaigners to those espousing the “great replacement theory,” which falsely suggests politicians are using immigration to try to replace white people across the West. Meanwhile, trust in public institutions, such as the police, politicians and the media, has nosedived in the United Kingdom, the U.S. and elsewhere.

And it’s from this online maelstrom of suspicion and misinformation that flare-ups such as the one in Southport emerge, Katwala said. Such online forms of communication allow those extremist viewpoints to become “more visible, more mobilized, more angry,” he said.

“It’s shrinking and fragmented, but it’s also socialized online, because it has spaces that belong to it where this stuff can seem normal.”

Alexander Smith

Alexander Smith is a senior reporter for NBC News Digital based in London.

Associated Press contributed.