Serious disorder has broken out in north Belfast for a second night.
Police used a water cannon after they were attacked by petrol bomb throwing crowds in the Carlisle Circus area.
According to the Northern Ireland Police Federation, which represents rank and file officers, nine PSNI officers have been injured and three taken to hospital so far this evening.
Almost 50 police officers were injured last night during hours of rioting linked to sectarian clashes in north Belfast.
A 17-year-old youth was arrested on suspicion of riotous behaviour.
Loyalists attacked police in the Carlisle Circus and Antrim Road areas during significant, but localised, violence linked to a republican parade.
The PSNI also deployed a water cannon in an attempt to disperse protesters, after the officers were attacked with fireworks, petrol bombs and masonry.
Four officers were taken to hospital with various injuries but only one of them remains in hospital. Another 43 officers were treated for various minor injuries.
Chief Superintendent George Clarke said: "I am both angry and sad that my officers have been subjected to such significant attack.
"They showed tremendous courage in the face of enduring violence."
A large crowd congregated between the Belfast Orange Hall and Carlisle Circus yesterday afternoon, where a lawful parade had been organised, however police had received no notification of a protest.
When police arrived on the scene some people within the crowd had masked their faces and police observed masonry being broken up by a number of individuals.
Police talked to community representatives with the aim of reducing tension and facilitating the lawful parade.
To allow the parade to pass along its notified route, police moved the crowd back towards Carlisle Circus.
Bricks and other missiles were exchanged between parade supporters and protesters as the procession passed through the area, but the most sustained violence was directed at police lines.
As the parade dispersed youths also began attacking police in the Antrim Road area.
Trouble continued throughout the night, until the area was reported calm at around 2am.
Chief Supt Clarke said people would be held to account for their actions.
"I am urging all individuals and communities affected by recent events to take a step back. Violence has serious and unwanted consequences for us all," he said.
"We must work harder at finding solutions through talking and accommodation.
"We cannot continue to see the lives of our community and our police officers put at such risk."
He added: "Every hour of disorder in Northern Ireland not only puts lives at risk, it also reduces confidence in our community and wastes huge amounts of money that could be better spent on schools and hospitals.
"Violence cannot be a solution."
PSNI Chief Constable Matt Baggott said Northern Ireland cannot afford a repeat of the violence.
He said his officers would continue to act as peacekeepers to keep communities safe, but he said others within the community and wider society have a responsibility to resolve conflict and tensions surrounding parading.