At least 15 people arrested after pro-Trump and anti-Trump protesters clashed in Berkeley, California

Thomson Reuters

Demonstrators in support of U.S. President Donald Trump gestures during a rally in Berkeley, California in Berkeley, California, U.S., April 15, 2017.

Right and left-wing protesters clashed on Saturday at a park in downtown Berkeley, California, exchanging blows and throwing bottles and cans as police in riot gear sought to separate the two camps, using explosive devices at one point.

At least 15 demonstrators were arrested during the brawls, according to NBC's Bay Area affiliate, and the police said they "anticipate more.

"There continues to be a number of large fights, some property damage and numerous projectiles being thrown, including fireworks," Berkeley police announced. 

And although a makeshift barrier had been raised between the two groups, it did not deter demonstrators.

The clashes broke out at an event originally organized as a so-called "Patriots Day" free speech rally and picnic by conservative activists. Several people appeared to suffer minor injuries. There were also reports of pepper spray and tear gas being used, as well as fireworks being thrown into the crowd. 

Photographs from the brawls show Trump supporters wearing "Make America Great Again" gear and using masks and helmets to cover their faces. 

Thomson Reuters

Demonstrators in support of U.S. President Donald Trump rally in Berkeley, California in Berkeley, California, U.S., April 15, 2017.

Demonstrators also used skateboards and helmets as weapons. 

 And although Berkeley police had specifically prohibited weapons like knives, bricks, rocks, glass bottles, and more from being brought to Civic Center Park, they confiscated a number of those items from people entering the area. 

"I wanted to show my support (for President Donald Trump)," said Daryl Tempesta, 52, who said he served in the U.S. Air Force near the end of the Cold War.

"As a veteran, I like the track America is on, and that Trump is willing to stand and say we are still America and we are not going to be globalist, we're not going to be a communist country. That's a message I can get behind," Tempesta said.

Among the counter-protesters were self-styled anarchists of the left, dressed in black and covering their faces with masks or bandanas.

As a result of the protests, which spread from the park to the streets, Berkeley's downtown BART station has been closed down.