An anti-hate rally has been disrupted when scores of anarchists wearing black clothing and masks stormed the demonstration in the Califorian city of Berkeley and attacked several supporters of President Donald Trump.
Police were able to head off any wider violence.
Thousands gathered on Sunday in response to a planned anti-Marxism protest that was cancelled amid concerns demonstrators might be attacked.
The counter-demonstration was largely peaceful for several hours until the antifa, or anti-fascists, overran police barricades around the protest area. The violence was swift but brief, and among those targeted was Joey Gibson, leader of the right-wing organisation Patriot Prayer that had called off a demonstration a day earlier in San Francisco.
Berkeley Police Chief Andrew Greenwood said officers were told not to actively confront the anarchists. He applauded officers' restraint, saying it forestalled greater violence. Six people suffered injuries, including two who were hospitalised, and one officer was injured while making an arrest and several others were hit with paint.
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There were 13 arrests on various charges including, assault with a deadly weapon.
