Violence has erupted in cities across the US on the sixth night of protests sparked by the death in police custody of African-American George Floyd.
Curfews have been imposed in nearly 40 cities, but people have largely ignored them, leading to tense stand-offs.
Riot police clashed with protesters in New York, Chicago, Philadelphia and Los Angeles, firing tear gas and pepper bullets to try to disperse the crowds.
Police vehicles were set on fire and shops were looted in several cities.
The National Guard – the US reserve military force for domestic emergencies – said on Sunday that 5,000 of its personnel had been activated in 15 states and Washington, DC, where crowds once again gathered near the White House, this time lighting fires and throwing stones at riot officers.
“State and local law enforcement agencies remain responsible for security,” the National Guard added.
Police in Washington DC have fired tear gas at demonstrators who set fire to properties near the White House. They include a historic church, St John’s Episcopal Church, known as the church of the presidents, near the White House.
It has emerged that in Friday night’s unrest, President Donald Trump was briefly taken by the secret service into an underground bunker at the White House, for his safety.
The US is witnessing the most widespread racial turbulence and civil unrest since the violent backlash to the assassination of Martin Luther King in 1968, says the BBC’s Nick Bryant.
More than 75 cities have seen protests, with streets only days ago deserted because of coronavirus, thronged with demonstrators marching shoulder to shoulder.
The Floyd case has reignited anger over police killings of black Americans. For many, the outrage also reflects years of frustration over socio-economic inequality and segregation, not least in Minneapolis itself, where George Floyd died.
There were many instances of police vehicles being vandalised and set alight on Sunday. Riot officers continued to respond with tear gas and flash grenades.
In Philadelphia, local TV stations showed people smashing police cars and looting at least one store.
Mr Trump tweeted: “Law & Order in Philadelphia, NOW! They are looting stores. Call in our great National Guard.”
Looting was also reported in Santa Monica, California.
At least 4,100 people have been arrested over several days of protests, according to a tally compiled by the Associated Press news agency. Arrests ranged from looting and blocking motorways to breaking curfew.
In Minneapolis, a lorry driver was arrested after reportedly breaching a road barrier before speeding towards a crowd of protesters marching along a major motorway. He has now been charged with assault, CNN reports.
Footage posted on social media showed dozens of people surrounding the vehicle and pulling the driver out from behind the wheel after it came to a stop.
The driver was later taken to hospital with minor injuries. There were no immediate reports of other casualties.
Minnesota’s Governor Tim Walz said the motive of the driver was unclear, adding: “To not have tragedy and many deaths is simply an amazing thing.”
In Denver, thousands of people protested peacefully in Colorado State Capitol by lying face down with their hands behind their backs and chanting: “I can’t breathe” – a reference to the circumstances of Mr Floyd’s death.
Large-scale protests also took place in Atlanta, Boston, Miami and Oklahoma City.
There were also several reported incidents of riot police responding disproportionately to the demonstrators. In Atlanta, Georgia, two officers were sacked on Sunday for using excessive force – including firing a taser – on two young college students.
A sacked white policeman has been charged with murdering Mr Floyd, 46, in Minneapolis.
Derek Chauvin, 44, is due to appear in court later on Monday.
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.