More than 100 protesters have marched through St Louis, stepping up pressure on a grand jury to charge a white police officer for shooting dead an unarmed black teenager.
Michael Brown was shot at least six times by Darren Wilson in the suburb of Ferguson on August 9, inflaming racial tensions.
The shooting sparked weeks of sometimes violent protests and a nationwide debate about police tactics, revived again with the death Sunday of a 12-year-old boy shot by police while waving what turned out to be toy gun in Cleveland.
Sunday's demonstration in St Louis was the largest of five consecutive nights of protests as the city braces for a decision expected by the end of the month from a grand jury on whether Wilson should be prosecuted.
"Hands up, don't shoot," and "This is what democracy looks like", chanted the crowd, banging drums and swaying to the rhythm of the words.
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Holding placards saying "Black Lives Matter", men and women of all ages and ethnic backgrounds went on a nearly two-hour march, weaving through the traffic.
Police have stepped up security as they brace for the grand jury announcement, with many residents fearing that protests could turn violent if Wilson is not indicted.
Outside the Buzz Westfall Justice Centre, where the grand jury has been meeting in the suburb of Clayton, metal interlocking fences and orange plastic barricades sealed off the building and the road.
St Louis County informed businesses and residents that they were securing buildings in downtown Clayton and temporarily restricting traffic in anticipation that protests could turn violent after the jury's announcement.
US President Barack Obama has called for calm. Missouri's governor has declared a state of emergency, and the FBI deployed extra personnel.
