Backers of Palestine Action have staged a series of protests since early July, when Parliament banned the group as a terrorist organisation.

Police in London have arrested some 150 people after demonstrators intentionally violated a new law banning support for a pro-Palestinian group because they say the legislation improperly restricts freedom of expression.

London’s Metropolitan Police posted on social media that officers are steadily working through the crowd and making further arrests.

Protesters gathered on Saturday afternoon in the square outside Parliament, with dozens displaying signs reading “I oppose genocide. I support Palestine Action.” That was enough for police to step in.

“Within this crowd a significant number of people are displaying placards expressing support for Palestine Action, which is a proscribed group,” the Metropolitan Police Service said. “Officers have moved in and are making arrests.”