Police officers have come under attack with bricks, bottles paintbombs and fireworks at a loyalist protest in south Belfast.
One police officer was injured and the force came under attack from missile throwers in the Lower Newtownards Road, Sandy Row and Shaw's Bridge areas. Several hundred people were involved.
About 200 people were involved in the disorder on the Newtownards Road. One man was arrested during the disturbances in the Sandy Row area as demonstrations continue against Belfast city council's decision to no longer fly the union flag 365 days a year.
There were also reports that a large loyalist crowd is rioting on the Lower Newtonards Road in east Belfast.
Earlier unionists had promised that a series of rush hour sit-down protests across key arterial routes around Belfast would be peaceful. They were designed to cause traffic chaos in the ongoing dispute over the restrictions on flying the flag at Belfast city hall.
The protests spread from Belfast into Pordown with one man being injured after a car was reported to have crashed into a group of loyalist demonstrators. The Police Service of Northern Ireland said that one man has been taken to hospital following the incident in the Co Armagh town.
There was a similar protest in a loyalist part of Derry with the main road into the city being blocked for a short period of time.
Meanwhile Christmas shoppers in a Tesco in Carrickfergus on the east Antrim coast where locked into the store on the advice of the police after disturbances broke out in the town. It has been the scene of some of the most violent loyalist protestors culminating in the firebombing of the Alliance Party's regional office in the town. Alliance was the party which pushed through a compromise on Belfast city council that led to the flying of the union flag for just 17 designated days of each year.
There are local reports that water cannon has been deployed tonight by the police to break up protests in Carrickfergus.
Northern Ireland has witnessed two weeks of demonstrations, some of them turning violent, by loyalists opposed to Belfast city council's decision to only fly the union flag on 17 designated days of the year. Until a fortnight ago the union flag was flown 365 days a year.
Traders have warned that the protests are endangering business, particularly in Belfast city centre, in the run-up to Christmas.
Northern Ireland Secretary Theresa Villiers met leaders of Northern Ireland political parties to discuss the flags controversy.
"I have today urged Northern Ireland's political leaders to come together to find a way forward to resolve the ongoing protests on flags," she said.
"It is vital that all the parties work together to make progress towards a cohesive and shared society where decisions on issues like flags can be made in a way which respects different views and takes into account the different traditions and identities of modern Northern Ireland."
She said she understood the strength of feeling but the disruption caused by these protests was damaging Northern Ireland's economy, particularly for retailers heavily dependent on shoppers in the run-up to Christmas.
"The fact that threats and protests continue to impede elected representatives in carrying out their duties also continues to be a major concern."
