A US police officer has been cleared of the manslaughter of an unarmed man and a woman who were killed after a high-speed car chase three years ago.

Officer Michael Brelo from Cleveland,was found to have acted reasonably when he shot the two black suspects - Malissa Williams and Timothy Russell - while standing on the hood of their car and firing through the windshield.

The white officer was also found not guilty of aggravated assault.

Judge John O'Donnell, quoted by Reuters, said Officer Brelo "was in a strange place at night surrounded by gunfire, sirens and flashing bulbs. Brelo did not fire too quickly or at a person who was clearly unarmed or unable to run him over. He did not fire at somebody running away."

A small group of demonstrators are reported to have gathered outside the courthouse to protest against the ruling.