By Brendan O'Brien

(Reuters) - Three Chicago police officers have been stripped of their law enforcement authority for their roles in the fatal shooting this week of a young black man who was found to have died of a bullet wound to the back, authorities said on Saturday.

The three policemen shot and killed the 18-year-old on Thursday after he sideswiped a squad car and another vehicle with a stolen Jaguar he was driving as police tried to arrest him, the Chicago Police Department said in a statement.

An autopsy on the man, identified as Paul O'Neal, determined he died from a gunshot wound to the back, according to records from the Cook County medical examiner showed.

Chicago Police Superintendent Eddie Johnson reviewed the incident on Friday, then relieved two of the officers of their authority and assigned them administrative positions, pending the outcome of internal and Independent Police Review Authority investigations, the department said in a statement.

"It appears that departmental policies may have been violated by at least two of the police officers," the department said. On Saturday, following release of the autopsy report, Johnson relieved the third officer of his police powers.

The swift actions, which go beyond mere suspensions from active police duty, appeared aimed at showing the chief's determination to swiftly address an apparent unjustified use of deadly force.

It came amid a flurry of high-profile deaths of unarmed black men at the hands of police in recent years that have raised tensions between minority communities and law enforcement as well as renewed a debate about racial discrimination in the U.S. criminal justice system.

Chicago police have come under criticism for some of those incidents, including the October 2014 slaying of Laquan McDonald, 17, who was shot 16 times by an officer.

Last week, the Independent Police Review Authority (IRPA) ruled that Chicago police used unjustified force last year when they shot and wounded a black suspect in an alleged drug transaction who drove off in his car when officers tried to stop him.

Three days after that incident, the department revised its deadly force policy, barring officers from shooting at moving vehicles if no other weapons were being used against police.

It remained unclear if a weapon was recovered at the scene of the incident on Thursday.

In July, IPRA released data showing a decline in Chicago police shootings while the use of electric stun guns, or Tasers, was up, suggesting training in non-lethal force was beginning to take hold in the department, which faces a federal investigation over its use of force and complaints of racial profiling.

(Reporting by Brendan O'Brien in Milwaukee and Steve Gorman in Los Angeles, editing by Larry King and Himani Sarkar)