Rioting has broken out in Belfast city centre again after hundreds of loyalists took to the streets to protest over flags.
A spokeswoman for the Police Service of Northern Ireland said: "Police are dealing with minor disturbances in the Shaftesbury Square area. The road is currently closed to any through traffic and diversions are in place."
Shaftesbury Square is an area near Queen's University which is popular with party goers.
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.
On Friday 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.
Police clashed with loyalists in Ian Paisley's home town of Ballymena, Co Antrim on Thursday.
There are plans to hold a major demonstration in Belfast city centre on Saturday - on what should be one of the busiest shopping days of the year.
During her visit 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.
On Wednesday a constituency office in Carrickfergus, Co Antrim was destroyed in an arson attack. An attempt to burn down Bangor premises occupied by the Alliance Party's Employment Minister Stephen Farry was thwarted.
Belfast city councillor Laura McNamee was also advised to leave her home while two others living in Bangor had their house vandalised.