BERKELEY (CBS SF) — Mayor of Berkeley Jesse Arreguin on Monday said it is time to confront the violent extremism on the left by treating black-clad Antifa protesters as a gang.

A large number of masked Antifa activists were seen jumping the barriers at a largely peaceful demonstration in Berkeley’s Martin Luther King Civic Center Park on Sunday.

Some began attacking Trump supporters at the rally.

“I think we should classify them as a gang,” said Arreguin. “They come dressed in uniforms. They have weapons, almost like a militia and I think we need to think about that in terms of our law enforcement approach.”

Arreguin said that while he does not support the far right, it was time to draw the line on the left as well, especially on the black-clad activists who showed up in force and took over both the protests and the park, and played a part in Sunday’s violent clashes.

“I think we are going to have to think ‘big picture’ about what is the strategy for how we are going to deal with these violent elements on the left as well,” said the mayor.

The mayor said it was also time for the non-violent protesters to take a stand.

“We also need to hold accountable and encourage people not to associate with these extremists because it empowers them and gives them cover,” said Arreguin.

On Monday, protest organizers defended Antifa’s presence.

“White supremacists and fascists are not welcome. And if the state is not going to protect us — and if they do not — then we are going to protect ourselves and welcome those who stand with us,” said Sara Kershner with the National Lawyers Guild.

KPIX 5 news crews observed that most of the conservative demonstrators in the park were Trump supporters who repeatedly denounced Nazis and racists.

And while it didn’t look good, the mayor also praised Berkeley police for holding back and ceding the park to the anarchists when the group jumped the barriers.

“Black Bloc was trying to provoke the police,” said Arreguin. “I think some of the more conservative protesters had already left or had been escorted out.”

When asked what he would say to a Trump supporter who was chased down the street, the mayor replied, “It’s unacceptable. Anyone who was injured… it’s completely unacceptable and we are going to be looking at video and identifying people.”

In the wake of Charlottesville and Sunday’s troubles in Berkeley, the mayor also called on UC Berkeley to call off next month’s Free Speech Week featuring Milo Yiannopoulos.

It was an appearance by Yiannopoulos in February that triggered a riot in Sproul Plaza on campus.

“I believe that is the right thing to do,” said Arreguin. “And if they don’t do that, then they need to work with the city and potentially assist the city through resources to be able to adequately police what we know is going to be a large protest that will spill out onto the city streets.”