Anger over the death of Freddie Gray while in police custody in Baltimore almost two weeks ago has sparked protests in a number of US cities.

Last night a line of police behind riot shields hurled smoke grenades and fired pepper balls at dozens of protesters to enforce a citywide curfew, imposed after the worst outbreak of rioting in Baltimore since 1968.

The racially charged violence on Monday by set off by the case of Freddie Gray, a 25-year-old black man who died of a spinal-cord injury under mysterious circumstances while in police custody.