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 dishonoring his memory and called on the National Guard to restore order.
Twitter accused Mr. Trump of glorifying violence in a post that said: “When the looting starts, the shooting starts.”
Mr. Floyd’s family has demanded that the four police officers implicated in his death face murder charges. Prosecutors have said they are still gathering evidence.
The incident has added to longstanding anger over the police killings of black Americans, including the recent case of Breonna Taylor in Kentucky.
There have also been demonstrations in other US cities, including New York, Los Angeles, Chicago, Denver, Phoenix, and Memphis.
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.”