Seven people have been arrested and eight police officers have been injured following clashes between loyalists and riot police.
The clashes have taken place near Belfast city centre as the controversy over changes to the flying of the Union Jack flag at the city hall continues.
The trouble broke out after a crowd attacked a van after its driver attempted to drive through a loyalist roadblock.
Police said an attempt had been made to hijack the van and missiles have been thrown at officers.
Traffic was disrupted in several areas of Belfast as small groups staged protests.
Incidents were also reported in Bangor and Lisburn.
The demonstrators have ignored calls from Northern Ireland's political leaders to suspend the protests.
In one incident a motorist became involved in an argument with demonstrators.
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."
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.