Four police officers were injured during clashes between pro-British and Irish nationalist youths in Belfast on Saturday following another protest against the decision to remove the British flag from city hall.
Nationalists threw golf balls and stones at a crowd walking home from a rally in the city centre demanding for the return of the flag. Police used water cannon and at least one plastic bullet round in a bid to restore calm.
The unrest over the past five weeks has been some of the most sustained in the British-ruled province since a 1998 peace deal ended 30 years of conflict between Catholic Irish nationalists seeking union with Ireland and Protestant loyalists determined to remain part of the United Kingdom.
Exposing a deep vein of discontent with the peace deal, loyalists have held nightly protests since councilors voted last month to end a century-old tradition of flying the British union flag every day over the city hall.
Loyalist politicians have joined their nationalist rivals in condemning the violence, but they have been unable to prevent groups of young men draped in British flags from clashing with police.
The protesters have complained that the removal of the flag was a step too far in the ebbing of loyalist dominance in the province, saying too many concessions had been given to Irish nationalists in a power-sharing government.
At least 1,000 loyalists, some with British flags and "No Surrender" banners, gathered at City Hall on Saturday. Hundreds of police were escorting them back towards east Belfast when the clashes began.
Reinforcements including dozens of jeeps, a helicopter and at least three water cannon trucks were sent in to try to control the crowds.