Several people have lost their lives during demonstrations seeking justice for a black man who died after a white police officer from Minneapolis forced his knee into the back of his neck.

They include a popular owner of a Louisville barbecue joint in Kentucky and a federal officer working security at an Oakland courthouse. Another was a person who go by the moniker "Mr. Indianapolis," a former popular football player.

Many of these fatalities have gone unnoticed, obscured by cities in the US reeling in chaos -- from steel baton-wielding riot police tactics to arson, vandalism and other forms of violent acts. Tens of thousands others have taken to the streets peacefully to demonstrate against police excessive use of force and racism.

Scores of American cities were gripped by chaos Monday night as demonstrators faced off with the authorities for a seventh consecutive night since the death of Floyd.

Curfews were enforced in New York City and in other parts of the country in efforts to prevent more fatalities, injuries and looting that have triggered more unrest that spilled into more violence. Almost 20,000 members of the US National Guard have been called up for deployment in 23 states.

The mayhem has reverberated in the streets of around 140 cities, and at least five people were reported to have died as the country was plunged into another long night of disorder.

An untold number more, which includes police officers, have been hurt. Police have arrested thousands of people as massive looting and arson caused millions of dollars in damages to businesses and properties.

Major chain stores, groceries, public government offices and police precincts have been damaged. Police vehicles have been set on fire across cities.

Dozens more have been injured in different forms of altercations - vehicles ramming into crowds, police officers sustaining head injuries and fractured bones and rioters being rushed to hospital emergency rooms with a variety of injuries from the clashes.

In the face of escalating protests -- from the beach areas of California to the local park located right outside the White House -- US President Donald Trump warned late Monday that he would use military force into American cities if mayors and governors fail to contain the mayhem.

Trump said, as reported in The New York Times by Campbell Robertson, Rick Rojas and Kate Taylor, that if a city or state fails to take the necessary measures needed to protect life and property of residents, then he said he will deploy the United States military to "quickly solve the problem for them."