Dozens of people have been arrested in protests in Cleveland after an officer was acquitted of the killing of a black couple.
Protests broke out on Saturday in the midwestern US city after patrolman Michael Brelo, 31, was found not guilty on two counts of voluntary manslaughter in the 2012 killings.
Police Chief Calvin Williams said 71 people were arrested, as multiple demonstrators broke away from the peaceful protests and in some cases assaulted bystanders.
"We only moved in to make arrests when things got violent and protesters refused to disperse," he told reporters.
"We wanted to make sure people understand we're going to help you in this process but if things turn violent, as we stated in the beginning, we will take action to preserve safety."
In one case, a protester threw a sign at a restaurant patron, while other demonstrators pepper-sprayed diners.
Cleveland Mayor Frank Jackson said authorities supported peaceful demonstrations but the city would make further arrests if necessary.
"We will and we continue to encourage a peaceful protest and demonstration, however, we will not tolerate activities that cross the line," Jackson said.
The verdict comes amid widespread tensions in the United States over police treatment of blacks following the deaths of a number of African Americans at the hands of law enforcement.
Brelo was one of 13 officers who opened fire on Timothy Russell and Malissa Williams.
A total of 137 rounds were fired at the car, including 49 by Brelo. He shot the final 15 from the hood of Russell's Chevrolet Malibu.
Brelo was also acquitted of felonious assault.
Cleveland Cavaliers star LeBron James called for calm after Saturday's demonstrations in his team's hometown.
Cleveland police were also under fire after Tamir Rice, a 12-year-old black boy carrying a toy gun, was fatally shot last year by an officer at a playground.
Take your Radio, Podcasts and Music with you
