Police have been injured as loyalists rioted in Belfast city centre after a controversial vote on the Union flag.
The violence spread to parts of east Belfast where loyalists who had earlier tried to smash their way into the grounds of City Hall attacked a Catholic church.
A police spokeswoman said reinforcements had to be called in to deal with the hundreds of loyalists throwing missiles, including fireworks, bricks and bottles. Five police officers, including two women, were injured during the disturbances. It is understood a press photographer was also taken to hospital for treatment to hand and facial injuries.
A Police Service of Northern Ireland (PSNI) spokeswoman said: "Five police officers have been injured, two of whom have been hospitalised. Two security staff of Belfast City Hall have also been injured."
Trouble broke out minutes after Belfast city councillors voted to remove the flag from City Hall. It is the first time the Union flag has been taken down from the Edwardian building since it opened in 1906.
Councillors agreed by 29 votes to 21 to bring City Hall into line with Stormont and other Government buildings and fly the flag on 17 designated days. Cars belonging to elected members and council staff were damaged during the disorder.
Sinn Fein Policing Board member Gerry Kelly said the PSNI had serious questions to answer about their operation.
The volatile situation in east Belfast had calmed by 11pm. The PSNI deployed its helicopter and riot squad officers in Land Rovers to monitor the large crowd gathered at Albertbridge Road and Newtownards Road.
Meanwhile, Northern Ireland Justice Minister David Ford added his condemnation. He said: "The violence which took place at the City Hall and round St Matthew's Church was the responsibility of two groups of people. The first is those who went to the City Hall spoiling for a fight, who attacked police officers and council staff.
"But there is a second group which bears responsibility. DUP and UUP politicians fomented this protest, with both leaflets and the use of social media. They called people on to the streets. They must have known, from experience as recent as this summer, that violence was almost inevitable. They cannot avoid their responsibility. Such violence should be condemned by all civic and community leaders."