More than 200 protesters carrying bullhorns, drums and signs demonstrated against police in Ferguson, Missouri, on Saturday night, with some placing the roasted head of a pig on a barricade in front of officers.

The protest in front of police headquarters took on elements of a street carnival ahead of the first anniversary of the fatal shooting of unarmed black teenager Michael Brown by a white officer in the city.

Demonstrators of all ages, with some children in the group, blocked traffic but were mostly peaceful. Some danced on cars and others stood on concrete barriers, cursing at officers through bullhorns.

Police mostly stayed behind a barricade.

"The whole idea is for people to be able to vent, to express themselves," said Ferguson police Sergeant Dominica Fuller, one of five African-Americans on the 50-member police force.

"They are getting their message out," Fuller said.

One group of protesters carved up a barbecued pig and placed its head on the barricade in front of officers.

Civil rights activists, religious leaders and others from around the United States have converged on Ferguson, a mostly black community of about 21,000 people, to commemorate the life and death of 18-year-old Brown, who was unarmed when he was shot in a confrontation with a white police officer on August 9, 2014.

The public events, many organized by Brown's father, include a moment of silence at midday on Sunday on the street where Brown died.

"I am out here because I never want what happened to Mike Brown to happen to a friend of mine or their kids," said Christopher Woods, a 34-year-old white Fergusonresident who said many of his friends are black.

The death of Brown and other African-American men in encounters with police sparked months of sometimes unruly protests in Ferguson and around the United States.

It also strengthened the "Black Lives Matter" movement that has cast a spotlight on long-troubled relations between police and minority residents of many US cities.

Ferguson Mayor James Knowles has said the city has made many reforms in the last year, though it still has more to do.