Thirteen men were arrested Saturday in the ethnically-mixed city of Bradford as a far-right, anti-Islamist group clashed with anti-fascist demonstrators in the streets.
Members of the English Defence League (EDL) threw bottles, stones and smoke bombs during violent scenes as police struggled to keep the two sides apart.
A heavy police presence largely contained the stand-off but the protest raised fears of a repeat of race riots that rocked Bradford in 2001.
The government banned the EDL from marching through the northern English city amid fears of unrest.
They staged a "static" demonstration in a small area in the centre of the Yorkshire city, home to one of Britain's largest Pakistani communities, against what they claim is the expansion of radical Islam in Britain.