Armed riot police moved in tonight to remove nationalist protesters staging a sit-down demonstration ahead of an Orange Order march.
The major security operation at the Ardoyne shops interface in north Belfast saw officers in body armour try to clear the Crumlin Road of more than 100 people who had been there from mid-afternoon.
Their initial attempts were resisted but the efforts were ongoing.
The protest at the notorious flashpoint was organised to prevent Orangemen marching along the road on their way back from the annual Protestant Twelfth of July commemorations.
A police helicopter hovered overhead while fortified land rovers surrounded the area as the tactical support group moved in.
The operation came after three police officers were shot last night during a night of rioting in the city.
The two policemen and one policewoman were blasted with a shotgun fired by a masked man who emerged from a crowd of nationalists who attacked the police as traditional Protestant 11th Night celebrations took place across the North.
Another 24 officers sustained injuries in two separate flashpoints in north and south-west Belfast.
Police said none of the injuries were life-threatening.
The shots were fired in the North Queen Street area, north of the city centre. There was also disorder in the Broadway area in south-west Belfast when around 200 rioters attacked police with missiles and petrol bombs.
Police responded by firing a number of baton rounds and deploying a water cannon.
The Police Ombudsman is investigating the police response in line with established protocol.
Elsewhere in the city, bomb disposal experts were examining a hijacked bus that was left outside Woodburn police station.
Two masked men reportedly got on the vehicle in the Glencolin Walk area around 4pm, told the driver a device had been left on the top deck and ordered him to drive to the station.
A car was later hijacked in the Oldpark Road area and found abandoned on Alliance Avenue where officers were examining it.
There was sporadic violence in other place across the North during a day that saw thousands of Orangemen attend events to mark the victory of Protestant King William of Orange over the army of Catholic King James II at the Battle of the Boyne in 1690.
In Lurgan, Co Armagh, youths tried to set fire to the Belfast to Dublin train as it stopped at a level crossing.
The driver managed to drive to safety. It is understood none of the 55 passengers on board were hurt.
Police also came under attack from petrol bombers in the same area.
Meanwhile, in Armagh city a vehicle was reportedly set on fire as a large crowd of youths gathered in the Killylea Road area.