PROTESTS spread across the United States today over the police killing of unarmed black man George Floyd in Minneapolis on Monday – with a tweet from President Donald Trump threatening further state violence only inflaming anger in black communities.

Thousands took to the streets of the city on Thursday night in a peaceful march for justice, while in other parts clashes broke out and protesters torched a police station.

But the officer who killed him was charged with third-degree murder in a victory for mass protest.

Journalists trying to cover the unrest were arrested by the Minnesota State Patrol, with CNN reporter Omar Jimenez handcuffed and led away while on air.

A producer and a photojournalist for CNN were also taken away in handcuffs. The force said it was “clearing the streets and restoring order” and that they were soon released.

Protester Erika Atson, a black woman who said she remembered her brothers’ arrests as children on the false assumption that they had guns, said: “We don’t want to be here fighting against anyone. We don’t want to be hurt. We don’t want to cause any damage. We just want the police officer to be held accountable.”

Firefighters worked to tackle blazes in the city’s business district where many outlets were set alight, and the National Guard blocked access to central streets. 

Hundreds rallied in Phoenix, Arizona, carrying signs declaring “Silence is violence” and “Being black should not be a death sentence.” Police attacked demonstrators with pepper spray and rubber bullets and many responded by hurling rocks and bottles. 

Mr Trump tweeted that the Minneapolis protesters were “thugs” and warned: “When the looting starts, the shooting starts,” a quote from 1960s Miami police chief Walter Headley as part of a crackdown on “young hoodlums who have taken advantage of the civil rights campaign.” It is associated with state violence against black people by a police chief who added: “We don’t mind being accused of police brutality.”

Twitter covered the tweet with a warning that it violated its standards as it glorified violence, but allowed people to click through to it as it said seeing what the President had said was in the public interest.

Protests took place in New York, Columbus, Los Angeles, Denver and Memphis among other cities.

In Louisville, Kentucky, there were protests over the death of black woman Breonna Taylor, who was fatally shot in March when police raided her home after mistaking it for another person’s address.

Seven people were shot during the Louisville protests but police said they had not fired at anyone.

George Floyd was ordered out of his car and detained by police on Monday as they responded to reports that a forged banknote had been handed in at a nearby shop.

Officer Derek Chauvin knelt on Mr Floyd’s neck, and video shows him saying “I can’t breathe” before he passes out. He was pronounced dead at hospital. 

Chauvin, who had 18 previous complaints on his file, and three other officers were fired on Tuesday. Today Chauvin was charged with third-degree murder and manslaughter.

Today Hal Marx, mayor of Petal in Mississippi, rejected calls to resign after he tweeted that he could see “nothing unreasonable” in Floyd’s treatment, adding that anyone who can say “I can’t breathe” must be able to breathe and that the death was probably unrelated.