Thousands of people in New York and other US cities protested for a third night against the use of lethal force by police against minorities, as prosecutors pledged to consider charges against an officer in the killing of an unarmed black man last month.

The killing of 28-year-old Akai Gurley, who was gunned down in November by a police officer in a darkened public housing stairwell in Brooklyn, is the latest in an avalanche of deadly police actions across the country which many deem racially-biased.