Police have exchanged gunfire with looters and arrested more than 100 people after crowds swarmed Chicago's luxury commercial district.
Superintendent David Brown called the outbreak "pure criminality" and Mayor Lori Lightfoot sought to distance the incident from the "righteous uprising" in response to the death of George Floyd at the hands of Minneapolis police on May 25.
"This was not an organised protest. Rather this was an incident of pure criminality," Brown told a news conference.
At least 13 officers were injured and a security guard and a civilian were struck by gunfire.
Social media images showed storefronts bashed in and people fleeing with arms full of goods, with much of the action taking place along Michigan Avenue, the upscale commercial district known as the Magnificent Mile.
People were drawn by a number of social media posts encouraging looting in central Chicago after tensions flared following the police shooting of a man with a gun, Brown said.
As police questioned a 20-year-old suspect, he fled, firing at the pursuing officers. Police returned fire and shot the man, who was hospitalised and expected to survive.
"After the shooting, a crowd gathered. ... Tempers flared, fuelled by misinformation as (Monday) afternoon turned into evening," Brown said.
In response to the social media posts, police sent 400 officers into the area, where they were met by caravans of people arriving in cars.
As officers arrested one man carrying a cash register, shots were fired at them from a passing vehicle, and police fired back.
Brown pledged a police crackdown in central Chicago, assigning officers to 12-hour shifts and cancelling days off.
Australian Associated Press