WASHINGTON -- American cities erupted in violence and destruction in a seventh straight night of unrest, with several police officers shot or run over, amid boasts and threats from U.S. President Donald Trump to send in troops to "dominate the streets."

In New York, nonviolent protests Monday night were punctuated by people smashing shop windows near Rockefeller Center and breaching the doors of Macy's flagship store on 34th Street, littering the pavement with broken glass. An SUV plowed into a group of officers at a demonstration in Buffalo, injuring three, including a state trooper who suffered a broken leg and a shattered pelvis.

Demonstrations also broke out in such places as Philadelphia, where hundreds of protesters spilled onto a highway in the heart of the city; Atlanta, where police fired tear gas at demonstrators; and Nashville, where more than 60 National Guard members put down their riot shields at the request of peaceful protesters who had gathered in front of Tennessee's Capitol to honour George Floyd.

Bystander Sean Jones, who watched as people ransacked luxury stores in New York over the weekend, said: "People are doing this so next time, before they think about trying to kill another black person, they're going to be like, 'Damn, we don't want them out here doing this ... again."'

The unrest in Minneapolis appeared to stabilize on the same day Floyd's brother made an impassioned plea for peace at the spot where a white police officer, Derek Chauvin, put his knee on the handcuffed black man's neck until he stopped breathing last week.

Chauvin has been charged with murder. Minnesota Attorney General Keith Ellison said Tuesday that prosecutors were working as fast as they can to determine if the three other officers at the scene should be charged, too. All four have been fired.

The death toll from the unrest rose to at least nine, including two people killed in a Chicago suburb. More than 5,600 people nationwide have been arrested over the past week for such offences as stealing, blocking highways and breaking curfew, according to a count by The Associated Press.

Cities struggled to keep police in line and avoid instances of excessive force. The police chief in Louisville, Kentucky, was fired after a beloved restaurant owner was killed by police and National Guard members enforcing a curfew. In Richmond, Virginia, the police chief said officers who used tear gas on a group of peaceful protesters would be disciplined.

An officer was shot shortly before midnight near the Circus Circus casino in Las Vegas. Police had no immediate word on the officer's condition. Four officers were shot in St. Louis; they were expected to recover.

Trump, meanwhile, portrayed himself as a hard-nosed, law-and-order president, with police under federal command using tear gas to clear peaceful demonstrators from a park near the White House so that he could walk to a church and pose with a Bible.

Emerging after two days out of public view, he threatened from the White House Rose Garden to deploy "thousands and thousands" of U.S. troops.

The photo op at the house of worship known as the Church of the Presidents was condemned by Episcopal Bishop Mariann Edgar Budde.

"The president just used a Bible and one of the churches of my diocese as a backdrop for a message antithetical to the teachings of Jesus and everything that our church stands for," she said.

A senior White House official said Tuesday that despite Trump's threats, the goal was to pressure governors to deploy National Guard units. The president was not rushing to use the Insurrection Act to send in the military, according to the official, who spoke on condition of anonymity.

For nearly a week since Floyd's death, largely peaceful protests by day have turned to chaos at night.

"We have been sitting on a powder keg for some time and it has burst," Philadelphia Police Commissioner Danielle Outlaw said.

Trump warned that if governors don't deploy the National Guard in sufficient numbers to "dominate the streets," the U.S. military will step in to "quickly solve the problem for them."

"We have the greatest country in the world," the president declared. "We're going to keep it safe."

As Trump spoke, tear gas canisters could be heard exploding.

A military deployment by Trump to U.S. states would mark a stunning federal intervention rarely seen in modern American history. It drew comparisons to 1968, when Richard Nixon ran as the law-and-order candidate in the aftermath of riots following the assassination of the Rev. Martin Luther King Jr.

Trump made little effort to address the grievances of black Americans and others outraged by Floyd's death and the scourge of police brutality, undermining what his reelection campaign had hoped would be increased appeal to African American voters.

Federal law allows presidents to dispatch the military into states to suppress an insurrection or if a state is defying federal law, legal experts said. But officials in New York and other states asserted that the president does not have a unilateral right to send in troops against the will of local governments.

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Sullivan and Morrison reported from Minneapolis. Associated Press journalists across the U.S. contributed to this report