Nearly sixty anti-fascist protesters were arrested in London at a counter-demonstration against a rival rally by the British National Party.
A few hundred had turned out to oppose the far right.
The BNP had wanted to march to mark the recent killing of a British soldier in a south London street. Two men have now been charged with his murder.
Drummer Lee Rigby’s family had appealed for calm and warned against reprisal attacks against Muslims.
The BNP, which says it wants to rid Britain of Islam, defended its protest.
“We are fed up with our borders being abused by people coming into this country, abusing our goodwill, and we end up with a massacre of that poor lad last week,” said protest organiser Matthew Cooper.
Despite the arrests the anti-fascists said they were pleased to have blocked the far-right’s march.
“I am here to stop the fascists. My parents fought in a war to stop this, and we are not going to allow this to happen in our country. And certainly not hijack the horrific attack that happened last week for their own cause. It is despicable,” said anti-fascism protester Julian Lema.
The two sides were mostly kept apart but there were some scuffles and at least one injury.
Far-right marches in other cities reportedly attracted few people. Previous anti-Muslim demonstrations in the wake of the soldier’s murder have been widely condemned.
Thousands of people including the leader of the opposition have reportedly signed a letter to a newspaper denouncing attempts to whip up fear and violence against the Muslim community.