The appearance of the British National Party leader Nick Griffin on the BBC's Question Time programme prompted hundreds of anti-fascist demonstrators to gather outside BBC Television Centre in West London.
The demonstration outside the BBC building was organised by Unite Against Fascism. The group accused the BBC of "rolling out the red carpet" to Mr Griffin and said it feared an increase in the number of racist attacks.
The BBC has defended its decision to go ahead with the programme, saying that because Mr Griffin was elected as one of two BNP MEPs, it was right to invite him.
At one point around 25 protesters forced their way through the gates of Television Centre when security guards tried to let a car in.
Some protesters managed to get into one of the building's receptions close to the studio where the programme was being recorded.
BNP leader Nick Griffin was surrounded by bodyguards as he arrived at a back entrance. He said he was expecting "a fair old political rough and tumble."
Security guards removed a number of protesters from within the gates. The BBC said they were dealt with quickly and escorted from the building.
The Metropolitan Police reported six arrests during the protest.
The police lines were reinforced as the evening wore on. A Scotland Yard spokesman said three police officers had been injured. There were no reports of injuries among protesters.
The BBC said the protests would not affect the recording of the programme which got underway once the panel and audience members had cleared security.
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