Amid a presidential election campaign in which racial rhetoric has played a central role, the UN working group on people of African descent warned that blacks in the US were facing a "human rights crisis."

This has largely been fuelled by impunity for police officers who have killed a series of black men -- many of them unarmed -- across the country in recent months, the working group's report said. 

Those killings "and the trauma they create are reminiscent of the past racial terror of lynchings," said the report, which was presented to the United Nations Human Rights Council on Monday.