FILE PHOTO: A man reacts as police officers operate during the "Lift The Ban" rally organised by Defend Our Juries, challenging the British government's proscription of "Palestine Action" under anti-terrorism laws, in Parliament Square, in London, Britain, September 6, 2025. REUTERS/Carlos Jasso/File Photo

LONDON (Reuters) -British police said on Sunday they had arrested almost 900 people at a demonstration the previous day in support of Palestine Action, and the government appealed for people to stop demonstrating in support of the banned campaign group.

Britain proscribed Palestine Action under anti-terrorism legislation in July after some of its members broke into a Royal Air Force base and damaged military planes.

That followed vandalism and incidents targeting defence firms in Britain with links to Israel. The group accuses Prime Minister Keir Starmer's government of complicity in what it says are Israeli war crimes in Gaza.

Hundreds of Palestine Action supporters have since been arrested at demonstrations, many of them over the age of 60. London police said 890 had been held following a protest near parliament in central London on Saturday, the highest number of detentions from a single such protest to date.

Of those, 857 were detained for showing support for a banned group, while 17 were arrested for assaults on officers after police said the protest turned violent.

"The violence we encountered during the operation was coordinated and carried out by a group of people ... intent on creating as much disorder as possible," said Deputy Assistant Commissioner Claire Smart.

The protest organisers, a group called Defend Our Juries, said that among those arrested were priests, war veterans and healthcare workers, and that they included many elderly and some disabled.

"These mass acts of defiance will continue until the ban is lifted," a spokesperson said.

Palestine Action's proscription puts the group alongside al Qaeda and Islamic State, making it a crime to support or belong to the organisation, punishable by up to 14 years in prison.

Human rights groups have criticised the ban as disproportionate and say it limits the freedom of expression of peaceful protesters.

Defence minister John Healey said the firm action was needed to counter accusations by right-wing critics of "a two-tier policing and justice system".

"Almost everyone shares the agony when we see the images from Gaza ... and for people who want to voice their concern and protest, I applaud them," he told Sky News. "But that does not require them to link it to support for Palestine Action, a proscribed group."

Many of those arrested in recent weeks are released on police bail, and it was unclear how many were still in detention.

(Reporting by Michael Holden; Editing by Aidan Lewis)