Phoenix, Arizona - Police in Phoenix, one of the biggest cities in the US, routinely use excessive force, a damning government report said Thursday – the latest condemnation of problematic behavior by American law enforcement.

Officers in the Arizona state capital rapidly escalate tensions in encounters with the public, resorting to sometimes deadly action within minutes of arriving on scene, the Justice Department said.

They also target ethnic minorities, the homeless, people suffering mental health episodes, and groups protesting police action, in what the Department of Justice described as a "systemic problem."

"The Phoenix Police Department uses excessive force, often unreasonably escalating the level of force within the very first few minutes or even seconds of an encounter," Assistant Attorney General for Civil Rights Kristen Clarke told reporters.

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"For example, Phoenix officers shot a man, and after he fell, fired multiple projectiles at him and then sent a police canine to drag him back to them. "The pain they inflicted was extraordinary, but for nine minutes, officers failed to provide medical aid. Tragically, that man died."

The three-year report, compiled from interviews, ride-alongs, and a review of bodycam footage, calls for a full overhaul of policing in Phoenix, the fifth most populous US city.

It comes after similar reports on problems in Minneapolis and Louisville and as tensions simmer between those who say US police routinely abuse their authority and those who say not enough is done to support people doing a tough job.

Thursday's report found that Phoenix police have one of the highest rates of deadly shootings in the country and rely on "dangerous tactics" and a wrong-headed notion of de-escalation.

"The Phoenix Police Department trains officers that escalation is de-escalation– meaning that you could escalate a situation with force, including deadly force, in order to defuse it," Clarke said.

The department also actively encourages officers to use their service weapons and has even "adopted a 'use it or lose it' policy, taking the weapons away from officers who did not fire them enough," she noted.

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The city of Phoenix has previously bristled at Justice Department oversight, insisting that the police department was aware of problems and had demonstrated "a powerful commitment to reform."

But Clarke said the issues raised in the report show that it was right for the federal government to step in.

"This is one instance where we can't count on the police to police themselves," she said. "Our findings today were very significant and severe violations of federal law and the Constitution."

In a statement issued Thursday, an hour after the report was made public, the City of Phoenix said it would review the findings before responding in detail.

"The Phoenix Police Department has demonstrated an ongoing commitment to continuous improvement by enhancing policy, accountability and training," the statement said.