British police arrested more than 160 people in east London on Saturday during rival protests by hundreds of anti-Islamist activists and thousands of counter-demonstrators.
The area is home to one of Britain's largest Muslim communities.
Reuters reports about 3000 officers were deployed to keep a group of 500 members of the right-wing English Defence League, apart from a larger group of anti-racist protesters.
Police formed lines across the streets to prevent the defence league marching to the borough of Tower Hamlets, which has a large Muslim community, and to keep the counter-demonstrators in their assigned area.
