Swedish climate activist Greta Thunberg was arrested Tuesday in London's financial district after displaying a placard in support of prisoners affiliated with Palestine Action, an organization proscribed by the U.K. government, according to police and campaign groups. The detention occurred outside the offices of Aspen Insurance, a specialty insurer that protesters say provides services to Elbit Systems UK, a subsidiary of Israel's largest arms manufacturer.

The City of London Police said a 22-year-old woman was arrested for displaying a placard "in support of a proscribed organisation (in this case Palestine Action) contrary to section 13 of the Terrorism Act 2000." Video shared by campaigners showed Thunberg holding a sign reading, "I support the Palestine Action prisoners. I oppose genocide."

Police said the protest followed early-morning damage to a building on Fenchurch Street, where Aspen's offices are located. "A man and a woman have been arrested on suspicion of criminal damage," a police spokesperson said, adding that "hammers and red paint" were used and that the pair "glued themselves nearby." A third arrest followed later, the spokesperson said.

Campaign groups said the demonstration was organized in solidarity with Palestine Action-affiliated prisoners, several of whom are on hunger strike while awaiting trial for alleged offenses linked to protest activity before the group was banned. According to organizers, eight prisoners joined the hunger strike, with the first two now on their 52nd day; three have stopped due to severe health risks.

The protest targeted Aspen after campaigners alleged the insurer's links to Elbit Systems UK. Defend Our Juries said the action sought to highlight what it described as Aspen's "complicity in genocide." A Palestine Action spokesperson questioned the basis for Thunberg's arrest, saying it was unclear whether police had "made another one of their mistakes in interpreting the crazy ban on Palestine Action" or whether authorities had "turned anyone expressing support for prisoners locked up beyond the legal time limit for taking action to stop a genocide into alleged terrorists."

Thunberg, who has repeatedly criticized Israel's war in Gaza and previously joined flotilla campaigns, said in a statement: "It is up to the state to intervene, and put an end to this by meeting these reasonable demands that pave the way for the freedom of all those who choose to use their rights trying to stop a genocide, something the British state has failed to do themselves."

Families and supporters of the hunger strikers have pressed the government to engage. Campaigners said they have asked David Lammy to meet them, and lawyers sent a letter asserting that refusing a meeting failed to comply with Ministry of Justice policy on hunger strikes.