By Jan Wolfe

(Reuters) -The U.S. Justice Department has opened an investigation into whether police in Phoenix unlawfully have used deadly force, retaliated against peaceful protesters and violated the rights of homeless people in the latest such inquiry involving a major American city, officials said on Thursday.

Since President Joe Biden took office in January, the department also has launched civil rights investigations into police conduct in Minneapolis and Louisville, Kentucky. Those were among the U.S. cities where large 2020 protests were held after high-profile killings of Black people by police officers.

The inquiries mark a shift in the department’s focus under the Democrat Biden, who has made racial justice a priority in contrast with the administration of his Republican predecessor Donald Trump.

Phoenix, with a population of roughly 1.7 million, is Arizona’s capital and largest city – and the fifth most populous city in the United States.

Attorney General Merrick Garland and Kristen Clarke, head of the Justice Department’s Civil Rights Division, announced the investigation at a news conference. Garland said such probes are “aimed to promote transparency and accountability.”

Racial justice activists have accused Phoenix police of carrying out unlawful surveillance, arrests and malicious prosecutions of protesters. Last month, Phoenix police responding to a mental health call shot and killed a man who pointed an object at them that turned out to be a water gun, authorities said.

Clarke said the Phoenix investigation has the full support of the city’s mayor and police chief.

“We look forward to working together with the city and the Phoenix police department toward the shared goals of ensuring constitutional policing and fostering greater cooperation between law enforcement officers and the community that they serve,” Clarke said.

Justice Department lawyers have met with close to 1,000 community members in Minneapolis and Louisville, and received written messages from hundreds more, Clarke said. Justice Department lawyers have also met with command staff of police departments in Louisville and Minneapolis, Clarke added.

“We will take the same approach in Phoenix,” Clarke said.

Phoenix Mayor Kate Gallego in a statement welcomed the Justice Department review, adding, “Comprehensive reform of policing in the city of Phoenix has been my priority since the first day I took office.”

U.S. police use of force has been in the spotlight in the aftermath of a series of deadly incidents in various cities in recent years, with protests around the country following the death of a Black man named George Floyd in Minneapolis in June 2020 – a crime in which a police officer as been convicted of murder. Louisville officers last year fatally shot Breonna Taylor, an unarmed Black woman, in a botched raid.

Clarke said police officers must use their authority in a manner that does violate the constitutional rights of people, complies with federal civil rights laws and “respects human dignity.”

(Reporting by Jan Wolfe; Additional reporting by David Schwartz in Phoenix; Editing by Will Dunham, Scott Malone and Richard Chang)