WASHINGTON (AFP) - US Attorney-General Loretta Lynch on Monday (Dec 7) announced a federal civil rights probe into the Chicago police department's use of force, prompted by the 2014 shooting death of a black teenager.

The investigation comes amid rising tensions in the city following the release of a graphic dashcam video of the Oct 2014 incident that shows 17-year-old Laquan McDonald shot 16 times by a police officer.

"Our investigation is focused on use of force and accountability," Ms Lynch said.

"We'll be looking at how force including deadly force is handled, investigated and how officers are held accountable for that. That is our focus right now."

Police officer Jason Van Dyke was charged with first degree murder last month over McDonald's death.

Last week, Chicago Mayor Rahm Emanuel fired the city's police chief Garry McCarthy, saying public trust in his leadership had been "shaken and eroded".

Ms Lynch said lawyers from the Justice Department's civil rights division will lead the federal probe into the Chicago police force, which will be wider than a parallel US investigation into the fatal shooting of McDonald.

She said they will look into whether police in the midwestern US city "engaged in a pattern or practice of violations of the Constitution or federal law".

She added: "Specifically, we will examine a number of issues related to the CPD's use of force, including its use of deadly force; racial, ethnic and other disparities in its use of force; and its accountability mechanisms, such as its disciplinary actions and its handling of allegations of misconduct."

If unconstitutional practices are found, the Justice Department will seek court-enforced reforms of the police force, she said.