The number represents an incarceration rate of 762 per 100,000 residents, compared to 152 per 100,000 in Britain, 108 in Canada, and 91 in France, HRW said in a statement commenting on Justice Department figures also released Friday.

"The new incarceration figures confirm the United States as the world's leading jailer," said David Fahti, HRW's US program director.

"Americans should ask why the US locks up so many more people than do Canada, Britain, and other democracies," he added.

The newly released figures show a sharp racial imbalance in the US prison population, with blacks outnumbering whites by six to one.

Nearly 11 per cent of black men aged 30-34 are in prison, according to Justice Department figures.

HRW said blacks in the United States are 12 times more likely to be sent to jail for drug-related crimes than whites, even though drug use among the two races is about the same.