United Nations: Expressing concern over "disproportionate" number of young African-Americans killed in police encounters in the US, the UN rights chief has said the court's ruling in Ferguson shooting case has spotlighted fears of "institutionalised discrimination" in the country.

"I am deeply concerned at the disproportionate number of young African-Americans who die in encounters with police officers, as well as the disproportionate number of African Americans in US prisons and the disproportionate number of African-Americans on Death Row," UN High Commissioner for Human Rights, Zeid Raad Al Hussein said in a statement.

Zeid said the decision in the Michael Brown case has spotlighted broader concerns about institutionalised discrimination across the United States.

"It is clear that, at least among some sectors of the population, there is a deep and festering lack of confidence
in the fairness of the justice and law enforcement systems," he said, urging the US authorities to conduct in-depth examinations into how race-related issues are affecting law enforcement and the administration of justice, both at the federal and state levels.

18-year-old Brown was shot by police officer Darren Wilson, who is white, in the US town of Ferguson in August, sparking protests around the country and inflaming the debate surrounding the treatment of African-American men by US law enforcement.

In a widely watched and scrutinised decision, the grand jury decided not to indict Wilson, sparking protests across US states and wide-spread looting in Ferguson. While the High Commissioner did not comment on whether or not the verdict itself conformed to international law, he said that continuing reports of deadly encounters between police officers and members of the African-American community had repeatedly prompted concerns among respected national bodies and by UN bodies monitoring the implementation of international human rights treaties.

Zeid noted that just two weeks ago, Brown's parents had addressed the UN Committee against Torture, which is currently reviewing the US application of its obligations under the relevant Convention.

The grand jury's decision on November 24 comes just three days after a police officer fatally shot another 12-year-old African-American boy Tamir Rice who was wielding a non-lethal replica gun in Cleveland because he was holding a non-lethal replica gun.

Zeid noted that Rice's killing not only reiterated the racial disparity in deaths at the hands of US police officers but also placed the issue of gun-related deaths in the US back into focus. "In many countries, where real guns are not so easily available, police tend to view boys playing with replica guns as precisely what they are, rather than as a danger to be neutralised," he said.

Pointing to Article 9 of the UN's Basic Principles on the Use of Force and Firearms by Law Enforcement Officials, Zeid said that law enforcement officials were called upon to "not use firearms against persons except in self-defence or defence of others against the imminent threat of death or serious injury."

"In any event, intentional lethal use of firearms may only be made when strictly unavoidable in order to protect life," he said.