By Miesha Miller

(Reuters) – Clashes between anti-fascist and right-wing militants in Portland, Oregon on Saturday sent four people to the hospital including a police officer and led to at least four arrests, authorities said.

Police seized knives, clubs and pepper spray after running battles between members of the right-wing Patriot Prayer group and counterprotesters who had initially faced off at a downtown park. Patriot Prayer founder Joey Gibson is running for the U.S. Senate.

“We seized numerous weapons early on, and interceded and separated people when necessary,” Portland Deputy Police Chief Bob Day said in a statement late on Saturday.

“However, once projectiles, such as fireworks, eggs, rocks, bottles and construction equipment were thrown and people were injured, we ordered people to disperse,” Day said.

Officers used rubber ball grenades, pepper spray and pepper balls to clear the crowds from streets around a downtown park, police said.

Four people were taken to local hospitals, one of whom suffered serious but non-life-threatening injuries, police said. One officer suffered what was described as a non-serious injury from being hit by a projectile.

Police said more arrests may follow on charges including disorderly conduct, assault, theft, robbery and reckless burning after detectives review video of Saturday’s confrontations.

The four people arrested on Saturday were taken into custody in connection with criminal investigations that began before Saturday’s protests, police said.

(Reporting by Miesha Miller in New York; Editing by Daniel Wallis and Paul Simao)