LONDON — Tens of thousands of people descended on Britain’s capital on Saturday in what is expected to be the country’s largest far-right rally in decades, organized by anti-immigration activist Tommy Robinson.

The “Unite the Kingdom” rally comes amid a surge of nationalism in the U.K., a far-right party topping the polls, and the murder of American conservative activist Charlie Kirk — an assassination Robinson has used to mobilize support in the run-up to the event.

Robinson — whose real name is Stephen Yaxley-Lennon — has long inspired rallies of mostly white, mostly male followers shouting soccer-style chants against Islam and immigration.

He has billed the rally as Britain’s “largest free speech festival,” and posted a video on X Saturday morning of hundreds of people gathered in central London waving England’s flag and British Union Jacks.

Large crowds crossing Westminster Bridge toward the Houses of Parliament chanted: “Whose street? Our street,” and “The people united will never be defeated.” A group traveling from New Zealand also performed a haka, a ceremonial chanting dance of defiance that is a cherished cultural symbol of the country.

A crowd of Unite the Kingdom supporters attacked police officers with “projectiles,” police later said on X, adding that “a number of officers had been assaulted” as the group tried to enter a “sterile area” created to separate them from a smaller counterprotest organized by Stand Up to Racism.

Footage posted by the force showed police with riot shields pushing back a crowd of protesters.

Robinson had told attendees not to wear masks, drink alcohol or be violent.

“It’s not a time for riots,” he said in a video on X. “It’s not a time for violence. It’s a time where you come and you stand proudly for your country.”

The Metropolitan Police told NBC News they estimated there were about 110,000 people in attendance at the Unite the Kingdom protest, and 5,000 at the counterdemonstration.

British police urged Muslim Londoners not to alter their plans, despite a record of “anti-Muslim rhetoric and incidents of offensive chanting by a minority at previous marches.”

“There have been some suggestions that Muslim Londoners should change their behavior this Saturday, including not coming into town,” said Metropolitan Police Cmdr. Clair Haynes, who is in charge of the public order policing operation in London. “That is not our advice. Everyone should be able to feel safe traveling into and around London.”

With five Premier League soccer matches taking place in the capital the same day, more than 1,600 officers will be deployed, police said.

“The football lads are coming from everywhere,” said Robinson, who was released from prison in May after being jailed for contempt of court in October.

In a Thursday video to supporters about Kirk, who was fatally shot Wednesday while speaking at an event at a university in Utah, Robinson referred to “the bastard who has murdered him, or the organization, the corporation or the government it is that has killed him.”

“In honour of @charliekirk11 & in honour of freedom on the 13th we march,” he wrote in a separate post on X.

Hundreds of people gathered at a vigil in London on Friday night to mourn Kirk, 31, a father of two.

Steve Bannon, President Donald Trump’s former chief strategist, is listed to appear onstage at the rally on Saturday, along with right-wing commentator Joey Mannarino and a lawmaker from Germany’s far-right AfD party.

Canadian psychology professor Jordan Peterson is also in the lineup.

Britain’s far right has been emboldened as Reform UK, a party led by Trump ally Nigel Farage, tops the polls. Farage recently said he would deport 600,000 people if he wins the next election.

In recent months, English flags have increasingly appeared on lampposts, crosswalks and apartment windows — seen by some as patriotism and by others as linked to soccer hooliganism and racism.

A counterprotest was led by leftist lawmakers Zarah Sultana and Diane Abbott.

Footage posted by the group on X showed hundreds of people gathered chanting, “Refugees are welcome here.”

Nearly 900 people, many of them older than 60, were arrested under counterterrorism legislation at a London demonstration last weekend against the ban on the group Palestine Action.

The British government banned Palestine Action — which describes itself as a direct action movement that uses disruptive methods — as a terrorist organization in July, putting it alongside Al Qaeda and ISIS. Membership or support is now a criminal offense punishable by up to 14 years in prison.

That extends to acts such as wearing clothing, carrying items or holding placards that could reasonably be seen as showing affiliation with the group.