Seven people have been arrested after 56 police officers and two civilians were hurt in rioting last night in Belfast.
The seven people are being held on suspicion of riotous behaviour, disorderly behaviour and hijacking.
One of the remaining four injured police officers needing hospital treatment remains in hospital.
56 police officers and two civilians were hurt following loyalist protests against a republican parade to mark the anniversary of the introduction of internment in 1971.
Loyalists blocked the passing of the parade for around four hours before the PSNI managed to push protesters back towards the Shankill area.
Officers deployed water cannon and 26 plastic baton rounds were fired.
Vehicles were set on fire with shops and at least one licensed premises damaged.
Today's Apprentice Boys parade in Derry was peaceful, feeder parades are making their homeward journey through Belfast this evening.
The trouble broke out as the city hosts thousands of international visitors attending the World Police and Fire Games.
PSNI Chief Constable Matt Baggott said it was too early to establish whether there was paramilitary orchestration of the violence.
Less than a month ago, parts of Belfast were consumed by rioting, predominantly loyalist, triggered when Orangemen were prevented from parading past the nationalist Ardoyne area in the north of the city.
Parading tensions have also spread elsewhere in Northern Ireland with major controversy surrounding a planned Sinn Féin-backed commemoration event in the Co Tyrone town of Castlederg tomorrow for local IRA members killed during the conflict.
Former White House special envoy Dr Richard Haass is due to chair cross party talks in the autumn.
The talks are in a bid to find a resolution to the parading disputes and other outstanding issues as yet settled during the peace process.
Mr Baggott said the bravery of his officers had saved lives last night.
But Ulster Unionist Assembly member Michael Copeland, a representative from East Belfast, has claimed he and members of his family were assaulted by police in Royal Avenue.
Asked about that incident and any other claims of police heavy handedness, Mr Baggott urged people with complaints to contact the Police Ombudsman's office.
But he added: "You saw the scaffolding poles, the metal gratings from the drains, the breaking up of paving slabs, people on roof tops trying to burn houses, people trying to set light to vans and cars and trying to drive them at police lines."
Mr Baggott said "You know something - if you are in the middle of a riot and you choose to be there, I have little sympathy. If anybody has any concerns about police actions they can report to the ombudsman - I won't stand over bad behaviour - but you saw the magnificent way that police officers reacted last night, and their courage - that is the message that needs to go out today."
The chief constable said the violence had cast a shadow over the Police and Fire Games, but he insisted that the positive memories of the event would endure longer than the thuggery of rioters.
Mr Baggott urged leaders to press home the message that politics was the only way forward.
Ulster Unionist leader Mike Nesbitt said rioters threw a half brick at him while he was trying to speak to officers in Royal Avenue last night.
Mr Nesbitt said those loyalists who engaged in violence were aiding a republican cause.
Stormont's Justice Minister David Ford said there could be no excuse for last night's rioting.
He said: "Those people had no intention of peaceful protest, they lack self respect and they lack dignity."
Northern Ireland Secretary Theresa Villiers also condemned the rioters and said the violence was "shameful".
"After success for Northern Ireland this summer as host to both the G8 Summit (in Co Fermanagh in June) and the World Police and Fire Games, disorder on the streets is a hugely regrettable step backwards," said Ms Villiers.
Mr Baggott warned that the "prisons would be bulging" once the police had identified and arrested those responsible.