The violence in north Belfast lasted for several hours
The RUC chief constable has said he is investigating the possibility the IRA may have been behind Thursday night's violence in north Belfast.
Police said more than 100 officers were injured in serious rioting in Ardoyne.
The trouble began earlier when the RUC tried to clear nationalist protesters who blocked the route of local Orangemen returning home from their annual 12 July parades.
The chief constable was asked by BBC Northern Ireland's chief security correspondent Brian Rowan if the violence was orchestrated by the IRA.
Sir Ronnie responded by saying: "I would think that is a line we would want to pursue very rigorously."
He also said the trouble "was planned".
The violence came as negotiations are due to resume between the political parties and the British and Irish governments to resolve the current political impasse in the province.
Further talks are taking place at Weston Park in Staffordshire on Friday to resolve the outstanding issues of policing, decommissioning and demilitarisation.
Speaking on Friday about the overnight violence, Sir Ronnie said: "People do not spontaneously have to hand acid bombs, blast bombs, and angle grinders to cut down lampposts to block roads."
"This was orchestrated. I have little doubt about that."
He added that the police were examining video footage "to determine whether there were key individuals there and who those individuals were".
A total of 250 petrol bombs and two blast bombs were thrown during seven hours of violence. Police replied with almost 50 plastic bullets.
At one stage a petrol filling station was also set alight by rioters.
Nationalists have accused the police of brutality, but speaking on BBC Radio Ulster, Sir Ronnie said police had to act in the way they did.
"If they had not acted in the way they did, what we would have faced was the most serious intercommunal violence.
'Lives at risk'
"So often my officers are injected between these communities and although that was not the case yesterday, had we not been there I have no doubt that serious intercommunal violence would have been the result and lives would have been severely and imminently put at risk."
The violence has sparked a round of bitter recrimination between the two communities.
The area's Democratic Unionist Party MP, Nigel Dodds, said the violence was orchestrated by republicans.
"It was clear that there was orchestrated, planned violence which was viciously executed against the police," he said.
"I was on the ground and the reality is that what I saw were people who were determined that there should be trouble and violence in the area.
"This was a one-sided attack by a number of republican thugs."
However, the Sinn Fein assembly member for north Belfast, Gerry Kelly, denied the violence was organised.
He said people had been provoked.
"It was a peaceful protest, I was there," he said.
Rioters cut a lamppost down to block the road
"There were stewards on the ground, they were keeping things calm and the water cannon and batons were turned on them.
"Once you attack the stewards who are trying to calm the situation, how do those people then keep control?"
Ardoyne SDLP councillor Martin Morgan condemned what he called a heavy and provocative police operation.
"A more sensitive approach to policing could
have avoided the situation", he sai
-- Anonymous, July 13, 2001