(CNN) The police chief of Portland, Oregon, is calling for legislation banning masks worn by demonstrators after violent street clashes between rival protesters last weekend left eight people injured.

"In other states, you'll see that it's illegal to wear a mask during the commission of a crime," Police Bureau Chief Danielle Outlaw told reporters Wednesday, according to CNN affiliate KOIN. "I understand and we wholeheartedly support individuals' first amendment right to free speech, but we cannot allow ... people to use the guise of free speech to commit crimes."

Outlaw was referring to violent demonstrations that erupted Saturday, when, she said, masks worn by some protesters hindered officers' ability to identify suspects. Clashing protesters included anti-fascist -- or Antifa -- demonstrators and members of right-wing groups, such as the Proud Boys, according to CNN affiliates KOIN and KATU.

"Legislation would really be helpful -- prohibiting the wearing of mask during the commission of a crime," she said, referring to steps the city could take to head off such violence in the future.

"If you knew that you can be easily identified, do you think you would be as inclined to commit that act of violence or commit that crime?" Outlaw asked. "A lot of people are emboldened because they know they can't be identified."

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