Police have fired tear gas and rubber bullets during clashes with protesters in St Louis after a white former policeman was acquitted of murdering a black suspect.
A peaceful rally over Friday's not guilty verdict turned violent after police confronted a small group of demonstrators, three years after the shooting of another black suspect in the nearby suburb of Ferguson stirred nationwide anger and debate.
Officers fired tear gas as people broke windows at a library and two restaurants and threw bricks and water bottles at officers. Protesters also threw rocks and paint at the home of St. Louis Mayor Lyda Krewson, said Acting Police Commissioner Lawrence O'Toole.
Nine city officers and a state trooper were injured and at least 23 people were taken into custody, he said.
Following the violence, rock band U2 cancelled a concert scheduled for Saturday night in St Louis, citing safety concerns for fans who would have attended.
"We have been informed by the St Louis Police Department that they are not in a position to provide the standard protection for our audience as would be expected for an event of this size," U2 said in a joint statement with concert promoter Live Nation.
The verdict that ignited protests on Friday was the acquittal of former city policeman Jason Stockley, 36, who was found not guilty of the first-degree murder in the shooting death of Anthony Lamar Smith, 24, on December 20, 2011.
After the ruling, around 600 protesters marched from the courthouse through downtown St Louis, chanting "No justice, no peace" and "Hey hey! Ho ho! These killer cops have got to go!" Some held "Black Lives Matter" signs.
"I'm sad, I'm hurt, I'm mad," Reverend Clinton Stancil of the Wayman AME Church in St Louis said by telephone. "We haven't made any progress since Ferguson, that's clear. Cops can still kill us with impunity."