Greta Thunberg was arrested at a demonstration in support of the Palestine Action protesters who are on hunger strike in prison, according to the Prisoners for Palestine protest group.

The 22-year-old activist was detained in the City of London on Tuesday after attending the scene of the early-morning demonstration on Fenchurch Street, the BBC reported. 

In a video shared by the group, she could be seen holding a sign reading "I support the Palestine Action prisoners" and "I oppose genocide".

The Prisoners for Palestine protest group said it staged the demonstration outside the offices of Aspen Insurance, which it claimed provides services to Israeli-linked defense firm Elbit Systems.

Palestine Action was proscribed under UK terrorism legislation earlier this year, making it a criminal offence to support or express support for the group.

Greta described the activists on hunger strike as "political prisoners" in a video posted on her Instagram on Monday, adding the UK government should meet their demands to be released from custody and for charges to be dropped.

The protest comes after several imprisoned Palestine Action activists, including one who has refused to eat for 52 days, have been taken to hospital in recent days.

Since the hunger strike began on 2 November, a total of seven prisoners have been taken to hospital.