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 have been shot and injured in Missouri, and two people reported killed amid unrest in Chicago.
The circumstances of both incidents are unclear.
Meanwhile, dozens of major cities imposed overnight curfews on Monday night. New York City is under lockdown until 05:00 (09:00 GMT) on Tuesday and Washington DC has extended its curfew for another two nights.
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 will begin in the city at 20:00 (midnight GMT).
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.
Mr Trump then turned his attention to the national protests, which he blamed on “professional anarchists” and the anti-fascist group Antifa. On Sunday, he said he intended to designate Antifa as a terrorist organisation.
He called on cities and states to deploy the National Guard, the reserve military force that can be called on to intervene in domestic emergencies, “in sufficient numbers that we dominate the streets”. About 16,000 of its troops have been deployed to deal with the unrest so far.
Mr Trump added, “If a city or state refuses to take the actions that are necessary… then I’ll deploy the United States military and quickly solve the problem for them.”
“I want the organisers of this terror to be on notice that you’ll face severe criminal penalties,” he said.
His comments were met with swift criticism from senior Democrats. Joe Biden, the party’s presumptive presidential candidate, said Mr Trump “[was] using the American military against the American people”.