• Greta Thunberg was arrested in London for supporting Palestine Action prisoners.
• She held a placard stating "I support the Palestine Action prisoners. I oppose genocide."
• The protest was against the UK government's ban on Palestine Action and their treatment of hunger-striking prisoners.
• Thunberg's detention has sparked criticism of the UK's stance on free speech.
• The Palestine Action group has been designated as a terrorist organisation by the UK government.

Swedish climate activist Greta Thunberg was detained by UK police in London on Tuesday after participating in a demonstration supporting prisoners from Palestine Action, a group recently banned by the British government. Thunberg was arrested under the Terrorism Act for holding a placard that read, "I support the Palestine Action prisoners. I oppose genocide," during the protest outside Aspen Insurance's offices, which provide services to Israeli defense contractor Elbit Systems, according to Middle East Eye and Reuters.

The City of London Police confirmed that Thunberg was one of three individuals arrested during the protest for supporting a proscribed organization under Section 13 of the Terrorism Act 2000. This legal measure has been a contentious issue since the government's ban on Palestine Action in July, following incidents of vandalism involving the organization. Protesters were also reported to have used red paint to symbolize blood on the company's building, revealing strong sentiments towards the ongoing Israeli-Palestinian conflict, according to India Times and South China Morning Post.

Thunberg's arrest comes as part of a broader protest focused on the treatment of Palestine Action activists who are currently on hunger strike in UK prisons, with escalating health issues reported among the detainees. The demonstration aimed to draw attention to their plight and the British government's legislation against the group. Criticism of the UK's handling of the issue has been amplified by various human rights advocates, including Francesca Albanese, who condemned the arrest, stating that it further complicates the narrative surrounding human rights and governmental accountability, as reported by Al Jazeera and Anadolu Agency.

The situation has drawn significant media attention, with public figures and political commentators expressing their concerns over free speech implications in the UK, particularly in light of Thunberg's ongoing activism for climate and humanitarian issues. Thunberg's label as a "terrorist" supporter for merely advocating for imprisoned individuals has raised alarms about the limits of public protest in the country, according to BBC and Middle East Eye.