Occasionally, anti-Trump protesters threw fireworks. Police seized a host of sticks, wooden dowels and poles.
In one altercation, demonstrators threw a pot of beans at each other.
As with the other fights, it was eventually separated.
Several people were observed by a Reuters reporter with bloodied faces and minor injuries, but there was no official word on casualties from authorities.
Protests were held in dozens of cities across the United States on Saturday for the anti-Trump "Tax Day", but the Berkeley rally was about free speech, according to local news reports. Opposing groups quickly organised their own event. (One of his supporters, conservative commentator Gavin McInnes, defended him by saying the victim's clothing disqualified her as a woman.) But this is the "alternative facts" era, so the laughable transparence of the self-defense excuse hardly matters to those who spout it.
In March, Berkeley experienced similar brawls after several of the same groups planned rallies to protest and counterprotest.
Facebook killer takes his own life as police close in
Facebook wasn't made aware of a live video containing Stephens' confession until after it had ended, Osofsky said. Police picked up the trail in a chase that lasted 2 miles before Stephens took his own life, authorities said.
The Trump supporters are declaring victory after they managed to push the antifas back and bust some heads in. He said they were being audited. Signs and flags must also be held alone. Rep. Maxine Waters, D-Calif., said there's nothing to prevent Trump from releasing his income taxes and "the simple truth is he's got a lot to hide".
Accusations of antisemitism, he said, were used "to justify anti-white racism".
Trump supporters announced earlier in the week that they were holding a "Patriot Day" at the park at noon that would feature speeches by members of the alt-right, an amorphous fringe movement that uses internet memes, message boards and social media to spread a hodgepodge of racism, anti-Semitism, misogyny and xenophobia.
"That would be a good question for the chief of police", one officer said.
The anarchists are professional rioters who brag about "bashing fascists". "We've staffed accordingly and are preparing for a number of different contingencies", he said. The fact that Jeff Sessions, Trump's attorney general, has made a showy display out of his utter lack of interest in police accountability only makes this situation more worrisome.
Despite the disturbance and cancellation of a weekly farmer's market event, due to the event, a stand was still opened during the rallies. Nearby, volunteers at an "empathy tent" helped protesters from both sides. The campaign coincides with the US' mid-April tax filing deadline.
In Washington, protesters rallied on the west lawn of the Capitol before a march to the Lincoln Memorial.