British police have arrested dozens more people under anti-terrorism laws for demonstrating in support of Palestine Action, a pro-Palestinian group banned by the government as a terrorist organisation, Reuters reports.

Hundreds of demonstrators gathered near parliament in central London to protest against the ban, with many holding up signs that said: “I oppose genocide. I support Palestine Action.”

London’s Metropolitan Police said officers had begun arresting those expressing support for Palestine Action. Police did not say how many arrests were made, but a Reuters witness said dozens of people were detained.