Police fire water cannon at Belfast protesters

Northern Ireland's power-sharing government put aside factional differences on Thursday to call for calm after frustration among pro-British unionists over post-Brexit trade barriers helped trigger some of the worst violence in the region in years.

The White House joined the British and Irish governments in urging calm.

Police said on Thursday that in some instances adults had stood applauding and shouting support while youngsters committed crimes of violence.

A week of violence has injured 55 police officers and seen boys as young as 13 and 14 arrested on rioting charges.