British police on Saturday arrested at least 139 Palestine Action supporters, who protested in London and Edinburgh days ahead of a court appeal over the government's contentious ban of the group.

London's Metropolitan Police began detaining people shortly after hundreds started a lunchtime "mass action" outside the US Embassy, an AFP reporter witnessed.

The force said in an evening update that officers were "continuing to make arrests" as they confirmed that 139 had already been detained.

Police have arrested more than 4,000 people on suspicion of showing support for Palestine Action, according to campaigners, after the British government outlawed it under anti-terror laws in July 2025.

Many of those arrested, including senior citizens and Holocaust survivors, have displayed signs at rallies reading: "I oppose genocide. I support Palestine Action."

In July, hearings related to more than 2,000 of those cases were postponed until later this year.

"It is truly dystopian that there have now been over 4,000 arrests under terror laws for peaceful vigils," Protest organisers Defend Our Juries said in a statement.

The ban puts the group on a blacklist that also includes Palestinian militants Hamas and the Lebanese Iran-backed armed group Hezbollah.

It made membership of, or support for, Palestine Action a criminal offence punishable by up to 14 years in prison.

The group's co-founder Huda Ammori has legally challenged the ban, arguing it was "disproportionate" and infringed human rights.

The Supreme Court is set to hold a two-day hearing on the high-profile case from Wednesday, after the Court of Appeal in June ruled in the government's favour.

- 'Losing faith' -

Saturday's London protesters held banners bearing slogans such as "How is trying to stop a genocide a crime?" and "We are protesters, not terrorists."

Attendee Angie Zelter, 75, told AFP she had already been charged at least eight times at previous rallies but wanted to protest again ahead of the Supreme Court hearing.

"I am hoping they will come to their senses and agree PA (Palestine Action) should not have been proscribed," she said.

Marji Mansfield, 70, a retired financial adviser, said she had previously been arrested about 10 times.

"I am losing faith in the judicial system," she told AFP.

"If they lift the ban, it would be a way out for the government," Mansfield added, while noting there was currently "no sign" of the ban's reversal.

A bestselling Irish author, Sally Rooney, has entered the controversy, with her publisher Faber revealing this month it can no longer sell her books in the UK because of her support for the group.

Set up in 2020, Palestine Action's stated goal on its website -- blocked to UK internet users -- is to end "global participation in Israel's genocidal and apartheid regime".

It gained visibility after Israel began bombarding Gaza following the October 7, 2023, attack by fighters from Palestinian group Hamas in southern Israel.

Palestine Action has mainly targeted weapons factories in Britain, especially those belonging to the Israel-based defence group Elbit.

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