At least 20 arrests were reported in California after violence broke out during a rally on Saturday demanding President Donald Trump release his full IRS returns.

About 200 people were at a park in Berkeley when several fights broke out. Dozens of police officers in riot gear standing nearby quickly arrested one man. Others were arrested after several skirmishes.

Trump supporters announced earlier in the week that they were holding a "Patriot Day" at the Berkeley's Martin Luther King Jr. Civic Center Park at noon that would feature speeches by members of the alt-right. Counter-demonstrators then said they would hold a rally at the same place at 10 a.m.

Officials put up a makeshift barrier of plastic orange poles and orange fence mesh to separate the sides, but that came down after demonstrators began punching and kicking each other, while pepper spray and firecrackers were thrown into the crowd.

Demonstrators shouted at each other from a distance after the barrier was put back, the San Francisco Chronicle reported. The groups then left the park and walked on Berkeley streets with police closely following them.

Officers on Saturday confiscated sticks, knives, flagpoles and helmets and sticks with signs on them.

The charges for the 20 arrested “include arrests for assault with a deadly weapon and several other felony assaults,” the Berkeley police said in a statement.

Police also said in a statement that “more arrests will be pursued” after officials investigate social media and video footage.

The rally followed March 4 demonstrations at the same park planned by some of the same groups and that ended in violent clashes. Several people were injured and police arrested 10 demonstrators.

In February, protesters threw rocks, broke windows and set fires outside the University of California, Berkeley's student union building, where then-Breitbart News editor and provocateur Milo Yiannopoulos was set to speak. His presentation was cancelled.

The Associated Press contributed to this report.