St Louis: A protest over police use of force that started peacefully has grown increasingly chaotic with demonstrators breaking windows in central St. Louis in the US and others attempting to block a ramp to an interstate highway, police and witnesses say.

Police say they have an order for the crowd to disperse at one intersection after reports of significant property damage.

A man is treated after being pepper sprayed as police tried to clear a violent crowd. Credit:AP

"Officers in personal protection gear have arrived on the scene in Downtown to disperse unruly crowd," St Louis police said on Twitter on Sunday night.

Earlier in the evening, a handful of demonstrators threw bottles in response to a police officer making arrests, the first indication that the protest could turn violent as it did the previous two nights.