Some cities, including Minneapolis, Atlanta and Seattle, saw clashes with police, buildings and cars set afire, and looting.
By evening, many demonstrations had given way to another night of violence and destruction, with protesters ignoring curfews imposed in dozens of cities. Police used tear gas and stun grenades and fired rubber bullets in attempts to disperse the crowds.
Floyd, a 46-year-old black man, died in police custody last Monday. Video shows a Minneapolis police officer had his knee on Floyd's neck for nearly nine minutes shortly before his death.
Truck barrels into Minneapolis protesters
In Minneapolis, a semitrailer plowed through a crowd of protesters marching on an interstate highway near downtown that had been closed to traffic.
Authorities say no one was injured when the truck drove into the crowd at a high speed, westbound on Interstate Highway 35.
According to the Minnesota Department of Public Safety, the driver may have been unaware of the highway closure. "It appears the semi was on I-35W as authorities were closing the road. It didn't appear to drive through any barricades," the department tweeted.
Some protesters jumped on top of the truck, and as it stopped, they dragged the driver out of the front seat and started beating him. The driver, identified by police as Bogdan Vechirko of Otsego, Minn., is being held on probable cause for assault. He was taken to a hospital and is being treated for his injuries.
"He was driving a gas tanker," said Rhys Gailah, 39, who was in the middle of a sit-in listening to speakers when the truck came barreling through. "He came driving at least 50 miles per hour through the crowd. Everyone was sitting. It was peaceful."
State Public Safety Commissioner John Harrington says authorities had shut down the freeway so the protesters, who numbered from 4,000 to 5,000, could safely demonstrate. Before the incident, the protest had appeared peaceful.
Tensions flare in the nation's capital
Protests continued in Washington, D.C., with marches from a historically black university to a park just across from the White House.
The peaceful marchers had a city police escort as they walked the nearly two miles from Howard University to Lafayette Square.
Protesters chanted about the death of Floyd and other African Americans who have died following police violence.
"Even in the middle of a pandemic, cops are killing us," read one sign carried by protester Elizabeth Betts.
"It's crazy how even in the middle of a pandemic, black people have to protest like this," she said. "We are at a point where it's the same story, the same things are happening. I'm tired of this."
The demonstration in Lafayette Park turned violent during the night, as protesters threw bottles at police, set fires to cars and to the basement of St. John's Church. The historic church has been attended by every president since James Madison.
Police pushed the crowds away from the White House with bursts of tear gas.
Washington, D.C., Mayor Muriel Bowser had established a citywide curfew from 11 p.m. to 6 a.m.
This is a breaking news story. This post will be updated.
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