Earlier in the day, another group of left-wing demonstrators dressed in black attacked at least three men in the park, kicking and punching them until the assaults were stopped by police. Police also used a smoke grenade to stop one scuffle.

Police in the San Francisco area have been braced for violence and trying to prevent protests that draw left-wing and right-wing opponents since the deadly confrontation in Charlottesville, Virginia, on August 12 during a rally of white supremacists.

Berkeley authorities did not issue a permit Sunday’s gathering of right-wing protesters and Berkeley Mayor Jesse Arreguin had urged counter-protesters to stay away.

It had been cancelled by organiser Amber Cummings, who encouraged supporters to stay away but said she would attend on her own.

By mid-afternoon Cummings had not appeared and left-wing protesters far outnumbered right-wing supporters.

Earlier in the day, police had set up barricades around park and checked people who entered to make sure they did not have prohibited items like baseball bats, dogs, skateboards and scarves or bandanas they could use to cover their faces.

Several people were arrested for violating rules against covering their faces or carrying items banned by authorities.

At one point, an anti-rally protester denounced a Latino man holding a “God Bless Donald Trump” sign.

“You are an immigrant,” said Karla Fonseca. “You should be ashamed of yourself.”

Several other people also yelled at the man, who said he was born in Mexico but supports Trump’s proposal to build a wall along the southern border.

Police pulled one supporter of President Donald Trump out of the park over a wall by his shirt as a crowd of about two dozen counter demonstrators surrounded him and chanted “Nazi go home” and pushed him toward the edge of the park. At least two people were detained by officers for wearing bandannas covering their faces.

Anti-rally protesters chanted slogans “No Trump. No KKK. No fascist USA” and carried signs that said: “Berkeley Stands United Against Hate.”

A separate group of counter protesters had assembled earlier Sunday at the nearby University of California, Berkeley campus and then marched park to merge with the anti-rally protesters who had already gathered there.

Both Cummings and Gibson have disavowed racism and say they wanted to hold the rallies to bring conservative voices to the liberal San Francisco Bay Area.

Student activism was born during the 1960s free-speech movement at Berkeley, when thousands of students at the university mobilised to demand that the school drop its ban on political activism.

However, the violence in Charlottesville led San Francisco area police and civil leaders to rethink their response to protests.