(CNN) Three people were arrested and eight people injured, including at least three police officers, during violent demonstrations in Portland on Saturday, according to police.

Multiple assaults were reported, police said, and items were thrown at demonstrators and officers that looked like milkshakes but contained quick-dry concrete.

Portland Fire & Rescue medics treated eight people on the scene, authorities said, including three police officers.

Two officers were pepper sprayed, an officer was punched in the arm by a demonstrator, and an officer sustained a head injury from a projectile, police said. The injuries were not life-threatening.

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