"The excessive use of force by law enforcement officials against racial and ethnic minorities is an ongoing issue of concern, particularly in light of the shooting of Michael Brown," said Noureddine Amir, who headed a review of the US by the UN Committee on the Elimination of Racial Discrimination.
"This is not an isolated event," Amir told reporters.
"It illustrates a big problem in the United States, such as racial bias among law enforcement officials, the lack of proper implementation of rules and regulations governing the use of force, and the inadequacy of training of law enforcement officials," he added.
Brown was shot at least six times by white policeman Darren Wilson as he walked down a street after leaving a store where police say he stole a box of cigars.
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Accounts differ widely, with police alleging Brown tried to grab Wilson's gun and witnesses saying he was shot with his hands up in a sign of surrender.
Although street protests have subsided, the debate over racial discrimination and distrust between African Americans and the police rages on.
A grand jury in St Louis is tasked with deciding whether to bring charges against 28-year-old Wilson, who is on paid leave.
"The United States must ensure that every case of excessive use of force is promptly and effectively investigated and the alleged perpetrators prosecuted and the victims or their families are adequately compensated," said Amir.
"It should undertake complete and comprehensive measures to address the root causes and avoid any future recurrence of such tragic incidents," he added.