Tens of thousands of protesters have joined two rival marches in London.

The Unite the Kingdom rally was organised by far-right figure Tommy Robinson, while the other was a pro-Palestine Nakba Day rally.

The Met said it had arrested 11 people “for a variety of offences” so far, but did not specify how many were linked to the Unite the Kingdom event and the pro-Palestine march.

More than 4000 police officers were deployed to the capital to manage a so-called “sterile zone” between the two marches.

Officers had drones, police horses and dogs, and armoured vehicles on standby, in an operation costing more than $8 million.

Fans of the Unite the Kingdom march waved Union flags, while protesters carried Palestine flags and signs reading “smash the far right” for the pro-Palestine rally.

Chants of “Keir Starmer’s a wanker” and “we want Starmer out” could be heard from the Unite the Kingdom march.

At the pro-Palestine march, a large group of protesters carrying banners and placards reading “Bristol stands with Palestine”, “Stop Trump, Stop Farage”, and “Free Palestinian Hostages” gathered with many wearing keffiyehs.

Robinson, whose real name is Stephen Yaxley-Lennon, posted on X on Saturday morning saying “today, we Unite The Kingdom and the West in the greatest patriotic display the world has ever seen”.

Later, he called for crowds to get involved in politics.

“Are you ready for the battle of Britain? 2029 we have an election. We’re not asking anyone to go out and fight, but this is the most important moment in our generation,” he told marchers.

Robinson also led protesters in a chant of support for technology billionaire Elon Musk, the world’s richest person. Musk spoke by video at a previous Unite the Kingdom rally. On Saturday, he reposted supportive messages on his social media platform X.

Meanwhile, Daniel Kebede, National Education Union general secretary, said “we’re marching today to show that we will not allow Tommy Robinson and the far right to divide our communities”.

Sabby Dhalu, Stand Up To Racism co-convener, said: “Violence broke out the last time Tommy Robinson’s Unite the Kingdom demonstration mobilised what was one of the largest far-right street demonstrations in recent British history.

“This comes amid wider attempts by figures such as Elon Musk to amplify far-right narratives and encourage political instability.

“The far right is attempting to exploit the cost-of-living crisis by stirring up racism and falsely blaming migrants and refugees for people’s hardships in order to build a dangerous street movement.

“History shows where this kind of politics can lead.”

Justice Secretary David Lammy said authorities would act “swiftly” if protests turned violent.

In a post on X on Saturday, he said: “The Unite the Kingdom march organisers are spreading hatred and division.

“They do not reflect the Britain I’m proud of. Peaceful protest is a fundamental right and one I will always protect.

“But if protest turns violent, we will act swiftly, with extra court capacity in place.”

-with AAP