Chicago's mayor has fired the city's police chief after a graphic video of an officer shooting a black teenager 16 times sparked a week of protest.

"The public trust in the leadership of the department has been shaken and eroded," Mayor Rahm Emanuel told reporters on Tuesday.

"Now is the time for fresh eyes and new leadership to confront the challenges," he said, adding that outgoing police Superintendent Garry McCarthy's record was nonetheless "a strong one and one he can be proud of."

Tensions flared after officials released a dashcam video last Tuesday showing police officer Jason Van Dyke kill Laquan McDonald by shooting him 16 times as the teenager walked away in October 2014.

The graphic video depicts the latest in a string of police shootings caught on camera to spark mass - and sometimes violent - protests.

The footage has fuelled an already acrimonious national debate about racism and the use of deadly force by officers.

Chicago police initially said that McDonald was high on the hallucinogen PCP, acting erratically and had lunged at officers with a knife when he was shot.

The city has come under intense criticism for refusing to release the video until ordered to do so by a judge following a Freedom of Information Act request.

Prosecutors charged Van Dyke with murder hours before the judge's deadline to release the video.

After spending the Thanksgiving holiday in jail, Van Dyke was freed on a $US1.5 million ($A2.07 million) bail on Monday.

It was the first time a Chicago police officer has been charged with first-degree murder for an on-duty fatality in more than 30 years.

There have also been accusations of a cover-up amid reports that police investigating the shooting deleted footage from security cameras at a nearby Burger King.