Protesters were to gather in the capital city of Columbia for a rally against the Confederate battle flag, a potent symbol of racism for many here.
Mourning for the nine black church members shot and killed by a suspected white supremacist at Charleston prayer service turned to anger over the flying of Confederate standard -- a subject of controversy for years.
Another demonstration, meanwhile, was planned in Charleston, site of the horrific murders, by organizers of the Black Lives Matter movement.
"It's time to put that symbol of rebellion and racism behind us and move toward healing and a better United States of America," said a petition on the left-leaning MoveOn.Org website that had gathered 320,000 signatures.
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The American and South Carolina state flags were set at half-staff after Wednesday's massacre at Emanuel African Methodist Episcopal church, where the victims included Clementa Pinckney, the chief pastor and a state senator.
Dylann Storm Roof, 21, from a small town outside Columbia, was apprehended the next day in North Carolina. He is currently in solitary confinement in Charleston, charged with murder.
In Charleston, meanwhile, professional cleaners were seen today at the Emanuel church where passersby continued to gather and lay flowers, ahead of Sunday services.
Thousands gathered Friday night for a city-organized vigil for the victims, aged 26 through 87, who Roof is accused of shooting with a handgun -- a weapon easily purchased in South Carolina, given the state's lax gun laws.
Holding hands, many with tears in their eyes, people sang the civil rights protest anthem "We Shall Overcome" in the College of Charleston basketball area.