The clashes started late Monday when a police car arrested a suspect and people started throwing stones at them in Rinkeby, north of Stockholm. Unidentified people, including some wearing masks, also set cars on fire and looted shops.

One officer was slightly injured when a rock hit his arm and one person was arrested for throwing rocks, police spokesman Lars Bystrom said Tuesday. Some civilians who tried to stop the looters were also assaulted, he added.

Another officer fired his gun, not as a warning shot but because he was “in a situation that demanded he used his firearm,” Bystrom said, adding “no one was hit.”

He declined to give further details, saying the episode would be investigated.