The situation in Belfast and other parts of County Antrim is quiet after some of the worst rioting for years.
Trouble broke out after the disputed Protestant Orange Order Whiterock Parade. Police returned live fire after being targeted by automatic weapons.
A man injured by a blast bomb is in a critical condition in hospital.
Secretary of State Peter Hain condemned the violence. "Attempted murder cannot in any way be justified," he said. He will meet NI's police chief on Monday.
Mr Hain said the rioting and attacks on the police and Army were totally unacceptable.
"There can be no ambiguity or excuse for breaking the law. All those with influence in the community, including the Orange Order and unionist politicians, must condemn this violence and give their full support to the PSNI.
"I will be meeting the chief constable, Sir Hugh Orde, tomorrow to receive a full report."
Sir Hugh said the Orange Order bore substantial responsibility for the rioting and attacks on his officers.
The Orange Order described his remarks as "inflammatory".
It said police actions were "brutal and heavy-handed".
In Belfast, police and Army came under gun attack from loyalist paramilitaries on a number of occasions and they returned live fire.
Police said youths blocked a road in east Belfast on Sunday morning.
They put up a barricade at the junction of the Albertbridge Road and Templemore Avenue, but the road has now reopened.
Ballymena is calm after serious rioting on the Larne Road.
Petrol bombs were thrown at the police and violence spread to Ahoghill, where youths gathered in the centre of the village, setting cars on fire, damaging houses and throwing fireworks at police.
Overnight, loyalist rioters attacked police with homemade bombs, guns and bricks, injuring at least six officers.
Cars were hijacked and roads were also blocked in Ballyclare, Glengormley, Rathcoole, Larne and Carrickfergus, as the violence spread.
In a statement, the Orange Order said it would not be speaking to the media until it had evaluated what had happened.
"While the Orange Order has noted the chief constable's intemperate, inflammatory and inaccurate remarks, we have decided to take a more responsible line and will not be drawn into a similar knee-jerk reaction," it said.
"At this stage, all we would say is that if what we saw today was policing, it was policing at its worst."
Sir Hugh Orde said his officers, and the Army troops called in to help them contain the violence over the Whiterock parade, were "heroes".
He said they had been attacked with petrol bombs and blast bombs in outbreaks of rioting.
Gunmen had opened fire on police and they had returned fire. At least six officers were injured and one civilian was shot.
"I have seen members of the Orange Order in their sashes attacking my officers. I have seen them standing next to masked men.
"That is simply not good enough," Sir Hugh said.
"The Orange Order must bear substantial responsibility for this. They publicly called people on to the streets."
"I think if you do that, you cannot then abdicate responsibility."
Meanwhile, civilians were also affected by road closures that brought chaos for hours.
The parade was re-routed to avoid the mainly nationalist Springfield Road area.
DUP leader Ian Paisley has criticised the Parades Commission for "refusing to consider other proposals" on the disputed Orange Order march from he and UUP leader Sir Reg Empey.
Sinn Fein President Gerry Adams said there had been "a concerted effort to attempt to draw young nationalists and republicans into the trouble".
The party said responsibility for the violence lies with comments made by the unionist leaders.
Sir Reg denied making any statements which he said could be construed as encouraging disorder. He condemned the trouble, but also criticised some of the police tactics.
Meanwhile, the SDLP has called on all political leaders and community representatives to restore calm on the streets.
Security minister Sean Woodward said he was appalled by what had happened overnight.
He said thugs were to blame for the violence on the streets and he praised the police for their handling of the situation.
The minister said extra resources to back up the police would be a matter for the chief constable.