Seattle police said on Saturday they were preparing for more weekend protests after a May Day march that turned violent when crowds hurled bottles and wrenches at officers, who responded with pepper spray and flash grenades.
Sixteen people were arrested in the violence, which erupted late Friday after a day of peaceful demonstrations to call attention to workers' rights, immigration issues and police treatment of minorities in the United States.
Three officers were hurt, including one who suffered a broken wrist and another with a dislocated shoulder, police said.
Law enforcement was ready in the event of more protests, department spokesman Drew Fowler said.