Thousands of people have marched to the Justice Department in Washington to call for stronger action against racially motivated crimes.
Demonstrators complained that black offenders are not given fair treatment
Civil rights leaders organised the demonstration following a series of racially charged incidents.
There have been several incidents of nooses being displayed - recalling racist lynchings in the southern US.
Black leaders say the noose incidents should be treated as hate crimes and the perpetrators prosecuted.
The marchers, most of whom were black, drew particular attention to charges brought against six black teenagers accused of beating a white student at a high school in Jena, Louisiana.
The attempted murder charges - which were later reduced - stemmed from a fight which broke out after white students hung nooses from a tree at the school.
No-one was charged with a crime for hanging the nooses, which sparked copycat acts in other parts of the US.
"When you hang up a noose, that's no joke to us. Our granddaddies swung on those nooses," civil rights campaigner Rev Al Sharpton told the crowd in Washington.
The Justice Department said it is aggressively investigating recent cases of noose hangings.
It said it has won 189 convictions on civil rights charges over the last year, more than ever before.
Prosecutors said they did not pursue such charges in the Jena case because they are not usually brought against minors, the Associated Press news agency reported.
Hate crimes are among several covered under civil rights violations.
Demonstrators in Washington also said they were angry at a justice system that locks up many more blacks than whites.
About one in three black men spend time in prison, compared to one in 17 white men, according to Justice Department statistics.
"The Justice Department wouldn't come to the people, we brought the people to the Justice Department," Rev Sharpton said.