Twenty-six officers have been injured while policing a protest organised by far-right activist Tommy Robinson, which saw up to 150,000 people march through central London.

Tensions flared at the Unite the Kingdom rally, with some protesters throwing bottles and other projectiles at police, the Metropolitan Police said – leaving four seriously hurt.

Tech billionaire Elon Musk spoke to protesters on Whitehall via videolink; while 5,000 people joined a nearby counter-protest organised by Stand Up To Racism.

The Met said 25 people had been arrested for a range of offences in what it described as “wholly unacceptable” violence.

A huge policing operation was put in place in central London with the Met deploying 1,000 officers and drafting in an extra 500 from other forces including Leicestershire, Nottinghamshire and Devon and Cornwall.

Assistant Commissioner Matt Twist said officers had “policed without fear or favour”, knowing it would be challenging.

“There is no doubt that many came to exercise their lawful right to protest, but there were many who came intent on violence,” he said.

Mr Twist said officers had suffered broken teeth, concussion, a prolapsed disc, a head injury and a possible broken nose.

“The 25 arrests we have made so far is just the start,” he added as the Met vowed to identify those involved in disorder.

Home Secretary Shabana Mahmood condemned “those who have attacked and injured police officers”.

“Anyone taking part in criminal activity will face the full force of the law,” she added.

Around mid-afternoon, the two demonstrations were divided on Whitehall by lines of police officers.

While the rally began largely peacefully, the Met said some officers had been attacked while trying to keep the two groups apart.

The Unite the Kingdom protest had “exceeded the estimates of organisers”, the force said, which meant there was not enough space for them all in Whitehall and Parliament Square.

Large crowds ignored police directions and tried to get into secure areas and spots occupied by those participating in the Stand Up To Racism protest.

“When officers intervened to block their path they were assaulted with kicks and punches,” the Met said – adding that riot police, horses and dogs were used to keep the opposing groups apart.

The Met also said people scaled fencing and scaffolding around Whitehall which put “themselves and others in danger”.

At one point, a glass bottle appeared to smash against a horse, causing the animal and rider to stagger backwards.

Scuffles broke out as police used batons to try and push back Robinson supporters gathered on the top of Whitehall and Trafalgar Square.

Robinson, whose real name is Stephen Yaxley-Lennon, addressed the crowds at the “freedom of speech festival” where he criticised politicians for “parroting” his ideas.

He also claimed UK courts had decided the rights of undocumented migrants superseded those of the “local community”.

Last month, the Court of Appeal overturned an injunction blocking asylum seekers being housed at The Bell Hotel in Epping, Essex.

Making a surprise appearance via videolink, Musk spoke about “massive uncontrolled migration” and called for a “change of government” in the UK.

“Something’s got to be done,” Musk said, as he was interviewed by Robinson.

“There’s got to be a dissolution of Parliament and a new vote held.”

TV presenter Katie Hopkins also spoke on stage after earlier appearing alongside Robinson, Laurence Fox and Ant Middleton at the front of the march near Waterloo station.

Nearby, at the Stand Up To Racism rally, independent MP Diane Abbott told demonstrators: “We know racism and violence and fascism is not new.

“But you know what? We have always defeated that racism and violence.”

Robinson brought his stage events to a close just after 18:30 and promised another such event.

The 42-year-old was released from prison earlier this year after being jailed in October for ignoring an order not to repeat false claims about a Syrian refugee, who had successfully sued him for libel.

Additional reporting by Daniel Sandford, Nick Johnson and Maia Davies.