Police deployed gas to disperse crowds in Phoenix, Arizona, after protesters outside a rally by U.S. President Donald Trump on Tuesday threw rocks and bottles, police said.
"People in the crowd have begun throwing rocks and bottles at police. They also dispersed some gas in the area," Phoenix Police Department spokesman Sergeant Jonathan Howard said.
"Police have responded with pepper balls and OC (oleoresin capsicum) spray in an attempt to disperse the crowd and stop the assaults," he said.
Police have not given an estimate of the number of protesters who turned out for the event, but Arizona media said there were several thousand people.
Media reports said some protesters had thrown bottles at police.