London police have arrested Swedish activist Greta Thunberg at a demonstration in support of pro-Palestinian hunger strikers.
"Greta Thunberg was arrested under the Terrorism Act at the Prisoners for Palestine lock-on protest," Prisoners for Palestine said in a statement on Tuesday.
Thunberg's arrest makes her the highest-profile person to be detained by police since the government banned the Palestine Action group under anti-terror laws.
Thunberg was holding a sign reading "I support the Palestine Action prisoners. I oppose genocide", it added.
The 22-year-old was among hundreds of people who boarded a flotilla in October that tried to break through the Israeli blockade of Gaza.
City of London Police said officers had arrested three people on suspicion of criminal damage at a building in London's financial quarter.
It said the arrests came after "hammers and red paint were used to damage a building".
"A man and a woman have been arrested on suspicion of criminal damage. They glued themselves nearby, and specialist officers are working to release them and bring them into police custody," a statement said.
"A little while later, a 22-year-old woman also attended the scene. She has been arrested for displaying an item (in this case a placard) in support of a proscribed organisation (in this case Palestine Action) contrary to Section 13 of the Terrorism Act 2000," it added.
The group was officially designated a "terrorist group" on July 5, 2025. Since then, at least 2,300 people have been arrested under terrorism legislation, with 254 charged solely for taking part in peaceful protests.
Some detainees are on hunger strike to protest at their treatment and call for their release on bail.
Two of the protesters began their hunger strikes in early November, according to their supporters, with others joining in the following weeks.
Amnesty and the civil liberties organisation Liberty are intervening in the case.
They say that the proscription marks a significant break from the UK’s traditional approach to protest movements that use direct action, and argue it breaches Articles 10 and 11 of the European Convention on Human Rights, which protect freedom of expression and freedom of assembly.
