(BBC) – A police station in Minneapolis has been set alight during a third night of protests over the death of an unarmed black man in custody on Monday.
A police officer was filmed kneeling on the neck of George Floyd, 46, despite him saying he could not breathe.
President Donald Trump said “thugs” were dishonouring his memory and called on the National Guard to restore order.
The incident has added to anger over police killings of black Americans, including Breonna Taylor in Kentucky.
Mr Floyd’s family have demanded that the four police officers implicated in his death face murder charges. Prosecutors have said they are still gathering evidence.
A CNN journalist, Omar Jimenez, and his camera crew were arrested live on air by Minnesota state police officers on Friday morning, apparently because they did not move on when instructed.
The team was released an hour later, after the governor apologised for the arrest.
There have also been demonstrations in other US cities, including New York, Los Angeles, Chicago, Denver, Phoenix and Memphis.
Twitter accused Mr Trump of glorifying violence in a post that said: “When the looting starts, the shooting starts.”
What is the latest in Minneapolis?
In the last few days, buildings have been burned to the ground or looted.
On Thursday, protesters gathered outside the police department’s 3rd Precinct, the epicentre of the unrest.
Officers fired tear gas and rubber bullets in an attempt to disperse the crowd. But the cordon around the police station, which is near where Mr Floyd died, was breached by protesters, who set fire to it and two other nearby buildings as the officers withdrew.
Minneapolis Mayor Jacob Frey said there had been no choice but to evacuate the police station, adding: “The symbolism of a building cannot outweigh the importance of life, of our officers or the public.”
He called the unrest “unacceptable”, but added that he and everyone else recognised there was “a lot of pain and anger”.
He spoke after a tweet from President Donald Trump blamed Thursday’s violence on a “lack of leadership” in Minneapolis and warned that he would send in the National Guard and “get the job done right” if Mr Frey failed to restore order.
National Guard personnel are normally under state control, although they can be put under federal control in emergencies.