Violent clashes broke out at a march by the Democratic Football Lads Alliance in central London on Saturday.
Dozens of DFLA supporters started fighting with baton-wielding police officers after trying to push past an escort while walking from Park Lane to Whitehall.
One was heard screaming “I’ll kill you” at a police officer, the Press Association reported.
Hundreds of others chanted: “Whose streets? Our streets.”
Scores of police officers on horseback and others wearing riot gear tried to control the most hostile marchers, with dozens of police vans used to block the crowd from breaking the agreed route.
Vans and riot officers had to separate DFLA marchers from anti-fascist counter-demonstrators, many of them masked, who shouted: “Nazi scum off our streets”.
At Trafalgar Square the DFLA supporters traded vicious insults with counter-demonstrators as riot police sought to keep them apart, bringing traffic around the famous landmark to a standstill.
The Metropolitan Police said it had made only one arrest so far.
March organisers had said on Facebook they were protesting against “returning jihadists”, “thousands of awol migrants” and “rape gangs and groomers”.
One demonstrator Peter Mantell, 53, from Crayford, said: “I detest some of the people I'm walking with. A lot of them hate people because of the colour of their skin.
“I'm a lefty. But I believe we should have a voice against the people who want to hurt everyone and cause harm.”
He added that he was a supporter of former English Defence League (EDL) leader Tommy Robinson.
Many members of the DFLA crowd appeared extremely angry with police, screaming at them for perceived inaction against “paedos and grooming gangs”.
The march concluded in Whitehall where a truck was used as a makeshift stage for speeches, but the small gathering lost momentum around 4pm.
One on-stage organiser claimed they were “set up” by police and anti-fascist protesters had blocked their walk.
At a separate rally held by counter-protesters, a message was read out from the Labour leader Jeremy Corbyn and the shadow home secretary Diane Abbott.
“Congratulations on today’s demonstration standing up against racism and far-right extremism,” they stated.
“We’re proud to walk in the traditions of anti-racism campaigners and activists. Your fight is our fight.”
