By Ian Graham
BELFAST (Reuters) - At least eight police officers were injured in Northern Ireland overnight in riots provoked by a decision to remove the British flag from Belfast City Hall, and police warned people against joining a protest there later on Saturday.
A wave of street violence since councilors voted on Monday to remove the flag is the most widespread by pro-British loyalists in years.
But loyalist political parties have condemned the rioting and it has not caused a split in the power-sharing government.
Dozens of youths, many draped in British flags, threw bricks and petrol bombs at police in Newtownabbey, a predominantly Protestant area 12 kilometers (8 miles) north of Belfast city center. At least two cars were stolen and burned.
Police responded with a water cannon and arrested seven people, including a 13-year-old boy.
Some of the fiercest overnight rioting was in the Shaftesbury Square area close to the city center. There was also unrest in the Ligoniel and Crumlin Road areas of north Belfast.
The British flag has flown above the provincial capital's city hall every day since it opened in 1906.
The decision means it will be flown only on 17 designated days including public holidays each year, as is the case at the provincial assembly at Stormont in the British-controlled province.
Pro-British politicians accused the loyalist paramilitary group the Ulster Volunteer Force of being behind the trouble and of using social media to organize riots.
Smaller protests took place across Belfast late on Friday, hours after a visit by U.S. Secretary of State Hillary Clinton, who said the violence showed the province's peace process was not yet complete.
At least 3,600 people were killed over three decades as Catholic nationalists seeking union with Ireland fought British security forces and mainly Protestant Loyalists determined to remain part of the United Kingdom.
A 1998 peace accord has mostly held, although militant nationalists have stepped up attacks in recent years and community relations remain fragile, with riots erupting every few months.
Assistant Chief Constable Will Kerr of the Senior Police Service of Northern Ireland said the disorder was putting lives at risk and urged people not to attend the demonstration later on Saturday.
"The risk to the public safety of all those involved is simply too great," he said.
(Reporting by Ian Graham and Conor Humphries; Editing by Tom Pfeiffer)