Police have reported fights, property damage and that protesters have thrown objects such as fireworks.
Police initially said 15 people were arrested.
Police in riot gear made at least 13 arrests and seized numerous prohibited items from the demonstrators by Saturday afternoon and indicated then that they anticipated more arrests would be made.
A white supremacist was caught on camera punching a woman as the supporters and detractors of President Donald Trump clashed in Berkeley, California. Small bands on both sides chased each other or brawled, sometimes with wooden planks, homemade shields, poles and pepper spray.
Protesters on each side held signs in support of their cause. The Oath Keepers told the Times they chose to be present at the rally to protect the Trump supporters.
A demonstrator against US President Donald Trump (R) snatches a sign from a conservative demonstrator during a Patriots Day Free Speech Rally in Berkeley, California, US, April 15, 2017.
Violence erupted between the opposing groups. But they were soon met with many black-clad, face-covered counter-demonstrators waving red-and-black anarchy flags, and clashes ensued.
And again in early March, when about 500 pro- and anti-Trump demonstrators punched, sprayed and clubbed one another, according to local news reports. "Rain or shine or fascism we will be here", said a young woman operating the cash register.
Protesters in Raleigh, North Carolina, said they suspect that Trump's returns might show he has paid little or nothing to the government he now heads, or that he was indebted to Russian, Chinese or other foreign interests.
"I feel we are going down the rabbit hole", he said.
Fireworks were thrown in the crowds; and sticks, flagpoles and other objects banned for the park were collected by police, who erected a plastic barricade between the two camps.
Trump was the first major-party nominee in more than 40 years not to release his tax returns, saying it was because he was under audit.
The attacker in video is dressed in the same shirt and carrying the same cross-body shoulder bag as Damigo during in the protest. Wyden, the ranking Democrat on the Senate finance committee, has introduced legislation that would require sitting presidents, including Trump, to release their tax returns for the past three years.