Loyalists blocked roads across Belfast tonight as part of a mass protest over flags.
The pickets caused disruption for rush-hour traffic. Bus operator Translink said it was suspending most of its Metro services into and out of the city centre.
Social media websites listed up to 60 protests across Northern Ireland to start from 6pm.
A PSNI spokeswoman said at least 10 roadblocks were ongoing.
She said: “A number of roads have been closed due to ongoing protests. These currently are Templemore Avenue; Albertbridge Road; Upper Malone Road at the Dub Lane; Crumlin Road at Cambrai Street and Hesketh Park; Limestone Road at North Queen Street and the Boyne Bridge off Sandy Row.”
It is the 19th day that loyalists have taken to the streets to show their opposition to restrictions on flying the Union flag over Belfast City Hall.
Most have been peaceful but sporadic violence has marred some of the demonstrations.
Meanwhile, two people were arrested after reports of disorder in east Belfast during the early hours of this morning.
Police said a group of about 15 men attacked houses in the Lower Newtownards Road area. A family left their home because of the attack.
Superintendent John McCaughan, of the PSNI, said: “Tensions are heightened; however, we would ask that people take a step back and consider the wider implications of engaging in any criminal behaviour.”