CHARLESTON - Several thousand people crowded onto one of the longest bridges in the Americas on Sunday and joined hands in a show of solidarity with the victims of the Charleston church massacre.

From Charleston to suburban Mount Pleasant, they formed a line across the Cooper River to forge what organisers called a Bridge to Peace Unity Chain nearly 4km long.

"It's not black lives that matter any more. All lives matter," said Black Lives Matter leader Jay Johnson to loud cheers from a mainly white crowd before the event kicked off. "We are united as the human race," he said.

Promoted on social media, the event was organised in a matter of days by local housewives and the chief of Mount Pleasant's police department.

"This incredible turnout says it all," said organiser Dorsey Fairbairn at the event, where a bagpiper played Amazing Grace, a chaplain read a prayer and vehicles crossing the span sounded their horns in solidarity.

Once up on the Arthur Ravenel Bridge and holding hands, participants observed nine minutes of silence - one for each of the victims of last Wednesday's bloodbath at Emanuel African Methodist Episcopal Church. The span, named for a South Carolina politician who once described the NAACP civil rights group as mentally retarded, is the third-longest cable-stayed bridge in the Western Hemisphere.

The mood was a joyful counterpoint to the sombre atmosphere at a two-hour Sunday service at the historic African-American sanctuary earlier in the day.

A 21-year-old white male, Dylann Roof, is charged with nine counts of murder in connection with the church shooting, which he reportedly hoped would ignite racial conflict.

Friends and families, both black and white, clapped hands and sang songs along the bridge, took souvenir selfies and wrote condolence messages in chalk on the pavement. They waved at a flotilla of small boats in the river below, hugged each other, exchanged high fives and lifted American flags into the breeze.

"This is how we do race riots in Charleston," quipped one man, using a dose of irony to sum up the cheerful mood.

The huge turnout contrasted with a protest at a park near the Emanuel church, billed as "a final burial of white supremacy", that attracted only about 40 people.

In another Charleston park on Sunday, a memorial for Confederate veterans of the Civil War was found vandalised with red spray paint.

AGENCE FRANCE PRESSE