It follows the death of unarmed black man George Floyd
Demonstrations have spread to more than 30 cities, with cars and buildings burned, shops looted and at least two people dead.
Curfews have been ordered in many areas to try and stem the violence.
The white former policeman who knelt on Mr Floyd's neck's due in court tomorrow charged with his murder in Minneapolis.
Mayor of neighbouring St Paul, Melvin Carter, says anyone looting and starting fires is hurting those already grieving:
