Peaceful May Day demonstrations in Seattle descended into violence when a rogue group of protesters threw bottles and firecrackers at police, who arrested nine people, authorities said on Friday.
Hundreds of protesters had marched in support of immigration rights and a rise in the minimum wage on Thursday afternoon, but early in the evening a second, "un-permitted" protest group began marching, police said on their website.
The rogue group set dumpsters on fire, and hurled bottles, bricks and firecrackers at officers, who used pepper spray in response, police said.
Rallies across the United States are planned every year on May 1 to mark International Labor Day by a coalition of organized labor activists, students, civil rights advocates and members of the clergy.
Last year, protests in Seattle also turned violent. Eight officers were injured and 17 protesters arrested.
(Reporting by Lindsay Dunsmuir in New York; Editing by Barbara Goldberg and Bernadette Baum)