President Donald Trump has threatened to send in the military to quell growing civil unrest in the US over the death of a black man in police custody.
He said if cities and states failed to control the protests and “defend their residents” he would deploy the army and “quickly solve the problem for them”.
Protests over the death of George Floyd have escalated over the past week.
Four police meanwhile were shot and injured on Monday night during unrest in St Louis, Missouri.
Police chief Colonel John Hayden Junior told reporters “some coward fired shots at officers and now we have four in hospital. Thank God they’re alive,” before becoming overcome with emotion.
Meanwhile, dozens of major cities have imposed overnight curfews.
In New York, the iconic department store Macy’s was broken into and a Nike store was looted, while other shop fronts and bank windows were smashed. Several people were arrested. Curfew in the city will resume at 20:00 (midnight GMT) on Tuesday.
The protests began after a video showed Mr Floyd, 46, being arrested in Minneapolis on 25 May and a white police officer continuing to kneel on his neck even after he pleaded that he could not breathe.
The officer, Derek Chauvin, has been charged with third-degree murder and will appear in court next week. Three other police officers have been fired.
The Floyd case has reignited deep-seated anger over police killings of black Americans and racism. It follows the high-profile cases of Michael Brown in Ferguson, Eric Garner in New York and others that have driven the Black Lives Matter movement.
For many, the outrage also reflects years of frustration over socio-economic inequality and discrimination, not least in Minneapolis itself.
The president delivered a brief address from the White House Rose Garden, amid the sound of a nearby protest being dispersed.
Mr Trump said “all Americans were rightly sickened and revolted by the brutal death of George Floyd” but said his memory must not be “drowned out by an angry mob”.
He described the scenes of looting and violence in the capital on Sunday as “a total disgrace” before pledging to bolster the city’s defences.
“I’m dispatching thousands and thousands of heavily armed soldiers, military personnel and law enforcement officers to stop the rioting, looting, vandalism, assaults and the wanton destruction of property,” he said.