Small-scale rioting broke out in Belfast city centre again tonight after hundreds of loyalists took to the streets to protest over flags.
A spokeswoman for the Police Service of Northern Ireland said they were dealing with "minor disturbances" in the Shaftesbury Square area.
The road, a popular nightspot near Queen's University, was closed to any through traffic and diversions are in place, she said.
Eye witnesses said officers were pelted with stones, bottles and other missiles.
Loyalists opposed to a restriction on the number of days the Union flag can be flown over Belfast City Hall have held protests across Northern Ireland every night this week despite appeals from the First Minister for them to be suspended.
Tonight demonstrations were also held in Bangor, Co Down, parts of south Belfast, throughout the north of the city and in Enniskillen, Co Fermanagh but police said there were no reports of violence.
Last night police clashed with loyalists in Ballymena, Co Antrim.
There are plans to hold a major demonstration in Belfast city centre tomorrow - on what should be one of the busiest shopping days of the year.
During her visit today US secretary of state Hillary Clinton appealed for the violence to stop.
Much of the anger has been directed towards the non-sectarian Alliance Party whose councillors in Belfast voted to limit the number of days the Union flag could be flown over the city hall from 365 to 17.
A death threat against the party's only MP, Naomi Long, marked a significant escalation in the seriousness of the sectarian tension.
Belfast city councillor Laura McNamee was also advised to leave her home while two others living in Bangor had their house vandalised.
PA