United Nations human rights experts on Friday called for a halt to racial profiling by US law enforcement officers and a review of laws allowing police to use lethal force.
The independent experts regretted that grand juries in the United States had failed to indict police officers for killing two unarmed black men in separate incidents that have led to mass protests.
Sending to trial the cases of Michael Brown in Ferguson, Missouri, and Eric Garner in New York would have brought all evidence to light and allowed justice to take its course, they said in a statement.
"I am concerned by the grand juries' decisions and the apparent conflicting evidence that exists relating to both incidents," said Rita Izsak, UN special rapporteur on minority issues.
"The decisions leave many with legitimate concerns relating to a pattern of impunity when the victims of excessive use of force come from African-American or other minority communities".
US Attorney General Eric Holder has mounted a civil rights review of the Missouri shooting and promised an investigation of the New York case.
Mutuma Ruteere, a Kenyan serving as UN special rapporteur on contemporary forms of racism, called for action in the face of what he called evidence of discriminatory practices including racial profiling by police officers.
"Such practices must be eradicated," he said.
International law allows the use of lethal force only where absolutely necessary to protect life, said Christof Heyns, UN special rapporteur on extrajudicial, summary or arbitrary executions.
"The laws of many of the states in the US are much more permissive, creating an atmosphere where there are not enough constraints on the use of force. A comprehensive review of the system is needed -- the enabling laws, the kinds of weapons the police use, the training they receive and the use of technology such as on-body cameras to ensure accountability," Heyns said.