Water cannon and extra British troops were last night being brought into the North as the conflict around a primary school in north Belfast continued.
More than 60 RUC officers have been injured in the disturbances, which have been taking place mostly in the Ardoyne area of north Belfast.
In rioting on Thursday night, 10 shots were fired at police and 24 officers were injured.
Six blast bombs, 46 petrol bombs as well as bricks, bottles and paint bombs were thrown at police and troops as they kept loyalists and nationalists apart.
There was no sign last night that the immediate cause of the trouble, a stand-off around a Catholic girls' primary school in the Ardoyne area of north Belfast, would be resolved.
A heavy police and army presence remained in the area.
Two Belgian water cannons arrived at Belfast port yesterday. The RUC would not say whether they had come in response to the disturbances in north Belfast but it is understood they had been ordered in preparation for the marching season and contentious march at Drumcree.
The British army press office said troop levels would rise to 15,200 over the next week. The normal figure was around 13,600.
But a spokesman said: "These troop movements form part of prudent contingency planning measures in connection with the forthcoming marching season."
He denied the rise was in response to recent disturbances.
Most of Thursday night's violence came from loyalists, who launched all the gun and blast-bomb attacks against the RUC.
Known paramilitaries were present within both nationalist and loyalist crowds, but the RUC Chief Constable said the attacks were more orchestrated among loyalist paramilitaries.
"That doesn't detract from the violence meted out by those on the nationalist side, but there's evidence of orchestration," Sir Ronnie Flanagan said.
Nationalists threw petrol bombs and fireworks at the RUC, but leading IRA members were seen attempting to keep order among the crowd.
"My officers are being targeted for murder in these gun and bomb attacks," Sir Ronnie said.
He compared the "men and women of the RUC with the scum that attack them, people whose mission in life is to fly flags and strut about in balaclavas thinking they are either Ireland's finest or Ulster's finest".
There were also indications that tensions were rising elsewhere.
In Ballymena, Co Antrim, troops patrolled the streets after loyalists protested at the flying of Tricolours in the nationalist Fisherwick estate.