BERKELEY, Calif. — At least four people were arrested after violence broke out Saturday between groups of supporters and detractors of President Donald Trump holding rallies in downtown Berkeley.

About 200 people were at Berkeley’s Martin Luther King Jr. Civic Center Park 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 they were holding a “Patriot Day” at the park at noon. Counter-demonstrators then said they would hold a rally at the same place at 10 a.m.

Police put in a makeshift barrier of plastic orange poles and orange fence mesh to separate both sides, but that quickly came down as demonstrators started punching and kicking each other, while pepper spray and firecrackers were thrown to the crowd.

The San Francisco Chronicle reports that after the barriers was put back in place, demonstrators shouted at each other from a distance.

“You go back to the ’60s,” shouted a pro-Trump supporter.

“You go back to the 1400s,” someone on the opposing side shouted back

The groups then left the park and walked on Berkeley streets with police closely following them.

Authorities had said ahead of the rallies, that baseball bats, sticks, flagpoles and any items that could be used as a weapon were banned at the park. Officers on Saturday confiscated sticks, knives, flagpoles and helmets and sticks with signs on them.

The rally followed a March 4 confrontation planned by some of the same groups that left several people injured and led to arrests.

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