They drew attention to charges against six black teenagers accused of beating a white student at a high school in Jena, Louisiana. The fight started after several white students hung nooses from a tree in front of the school.

The protestors demanded that the federal government intervene in the case and investigate the hanging of a noose at the school, a symbolic historic reference to the lynchings of blacks that took place in southern states in the early days of the civil rights movement.

“When you hang up a noose, that's no joke to us. Our granddaddies swung on those nooses. Every noose that's hung should be prosecuted by law,” a well known civil rights campaigner Rev. Al Sharpton told the crowd in Washington, explaining the emotional impact a noose hanging has among black people.

After the incident, no white student was charged. The charges against the black students were later reduced. On the other hand prosecutors say that no charges were brought in the Jena schools because the suspects were minors.

The blacks marching along Pennsylvania Avenue also asked for fair treatment from the justice system that locks up more blacks than whites. One in three black men is likely to spend time in prison, compared to one in 17 white men, according to Justice Department statistics.

“And look behind you all the way to the end of the plaza. From all over this country, we're here. The Justice Department wouldn't come to the people, we brought the people to the Justice Department," Rev Sharpton said.

US Attorney General Michael Mukasey, who began his first full day on the job Friday, said the Justice Department was investigating the series of hate crimes. "These symbols of hate have no place in our great county," he said in a statement.