Dozens of protesters have been arrested with hundreds more warned they face arrest on Saturday as pro-Palestine Action demonstrators gathered outside the US embassy.

The Metropolitan Police said demonstrators were “essentially meeting to purposefully commit a crime” and would face arrest over support for the group, which was proscribed under the Terrorism Act in June last year.

Footage from the protest shows hundreds of protesters holding Palestinian flags and banners, with police carrying away the first demonstrators arrested. The force said it has arrested 48 people so far and that officers are continuing to make arrests.

Reports suggest around 400 people are expected to attend the protest, which began at 1pm on Nine Elms Lane in Wandsworth.

Defend Our Juries said protesters will hold signs reading “I oppose genocide, I support Palestine Action”.

A Section 35 dispersal order is also in place in parts of central London from 8am to 11pm on Saturday due to the protest. It means police can order a person to leave the area or face arrest, where certain conditions apply.

In a statement ahead of the protest, the force said: “Anyone planning to attend a demonstration in support of Palestine Action in the vicinity of the US Embassy on Saturday, 31 October will face arrest as part of a robust policing operation. Expressing support for the group is an offence under the Terrorism Act following its proscription in June 2025, a decision upheld by the Court of Appeal in June 2026.”

Commander Adam Slonecki, who is leading the policing operation, said: “All those intending on coming to this event know that supporting a proscribed organisation is unlawful – they are essentially meeting to purposefully commit a crime.

“The public would rightly expect us to be proactive and not just standby and wait for offences to be committed.

“I want to be clear – it is not just those who hold up placards who should expect to be arrested. Anyone officers consider to be playing a key role in organising the event, giving instructions to others and/or providing logistical support will very likely be committing an offence and face enforcement action.”

He added the action was “not about preventing people from expressing their views” but about “acting robustly in cases where doing so involves criminality”.

“These events also take significant police resources away from the neighbourhoods and communities where they are most needed,” he continued. “I would urge anyone planning on attending to reconsider.”