cities on Sunday as curfews failed to quell violence that replaced peaceful daytime demonstrations over the death of a black man seen on video gasping for breath as a white Minneapolis police officer knelt on his neck.

Mayor Bill de Blasio said police conduct was being investigated, including widely shared videos showing a police sports utility vehicle in Brooklyn lurching forward into a crowd of protesters who were pelting the car with debris.

De Blasio said he had not seen another video showing an officer pulling down the mask of a black protester who had his hands in the air, then spraying a substance in his face.

Protests also flared in Chicago, Seattle, Salt Lake City, Cleveland, and Dallas, where rioters were seen on video beating a store owner who chased them with a large machete or sword.

In London, hundreds of protesters took to Trafalgar Square on Sunday chanting “no justice, no peace.” On Saturday, a crowd descended on the U.S.

The arrest on murder charges on Friday of Derek Chauvin, the police officer seen kneeling on Floyd’s neck, has failed to satisfy protesters.

The issue ignited in 2014 with the shooting death of a black 18-year-old, Michael Brown, by a white police officer in Ferguson, Missouri, where police fired tear gas at protesters on Saturday night.