Almost 30 police officers were injured after shots were fired during serious overnight disturbances in Belfast.
Police said a total of 27 officers were injured - 13 in the Broadway disturbances and 14 in North Queen Street, including the three who were shot - a woman and two men.
The acting chairman of the Northern Ireland Policing Board, Brian Rea, condemned the incidents.
"My thoughts are first and foremost with the family and colleagues of all the officers who were injured," he said.
"This is very shocking news and the level of violence directed at police must be condemned.
"At this time I would call for calm right across the community."
Three officers were wounded by shotgun pellets when nationalists attacked officers as the traditional Protestant 11th Night celebrations were taking place across Belfast.
Other officers suffered other injuries.
None of the injuries was thought to be life-threatening.
The night of disorder came amid fears of trouble during today's July 12 commemorations.
Police presence will be high at potential flashpoint areas as thousands of Orangemen parade to mark the annual Protestant festival.
Ulster Unionist MLA Basil McCrea, a member of the policing board, described last night's events as "nasty".
Mr McCrea told BBC Radio 4's Today programme: "It is worse than it has been for a number of years. There certainly seems to be a case where rival gangs were intent on having a go at each other, and the police were caught in the middle of all of this.
"There's an escalation in the sense that when somebody is using a firearm that is a serious turn of events.
"We have had trouble in Broadway for the last three or four nights and the concern is that it is organised by dissident republican people. It doesn't seem that is the case, although there is a lot of organisation going into it, because there were a lot of petrol bombs thrown."
He added: "The parades themselves, one hopes, will pass off peacefully. Normally they do, because there is a very large number of people out on the streets enjoying themselves.
"The problem, if it arises, usually arises in the evening when the bands are returning home and if they are in contentious areas then we might expect trouble. The danger is that that then sparks off trouble in other parts of the province."
The shots were fired in the North Queen Street area, north of the city centre. There was also disorder in the Broadway area in the south west of Belfast when around 200 nationalist rioters attacked police with missiles and petrol bombs.
Police responded by firing a number of baton rounds and deploying a water cannon.
Chief Superintendent Mark Hamilton condemned the disorder and attacks on officers.
"These officers were doing their jobs, were policing their local community and have been attacked whilst doing so," he said.
"This is utterly wrong and I condemn it in the strongest possible terms.
"We responded to this disorder immediately and officers put themselves in danger in order to restore normal and calm to the area for the residents who live there. No-one wants a return to this type of behaviour.
"I am very grateful to those in the community who took personal risk to try and prevent disorder and help the police in very difficult circumstances.
"We have appealed for calm in the run-up to the Twelfth of July and we continue to do so.
"We would appeal to anyone with influence in the community to exert it to ensure that the next few days pass off without incident.