Fresh concerns have been raised about the use of plastic bullets after the Police Ombudsman was notified that 17 have been fired during race-hate riots.
It is understood the projectiles, described by police as Attenuating Energy Projectiles (AEPs), were discharged since trouble erupted on Tuesday.
Race violence flared after a man in his 40s suffered serious injuries to his face, neck and back in a frenzied knife attack in a nationalist area of north Belfast on Monday.
A 30-year-old Sudanese man, Hadi Alodid, has been charged with attempted murder and possessing a bladed article in public.
There was serious rioting in parts of the north on Tuesday and Wednesday, when police used water cannon after a masked mob attacked their lines in Glengormley.
Riot officers were pelted with missiles while vehicles and a house were torched.
In Portadown, Co Armagh, petrol bombs were also thrown at the PSNI by masked youths.
Police say 12 officers have been injured since the violence broke out.
Senior loyalist figures are believed to involved in organising trouble at a local level in parts of Belfast.
A spokeswoman for the Police Ombudsman said: “We have been notified by police that ‘Attenuating Energy Projectiles’ have been used 17 times, and that water cannon has also been used during this week’s public disorder.
“Each incident will now be assessed by Police Ombudsman investigators.”
The United Campaign Against Plastic Bullets has now raised concerns about the continued use of plastic bullets.
Mark Kelly, whose 12-year-old sister Carol Ann Kelly, was shot dead by a plastic bullet fired by a British soldier in Twinbrook, on the outskirts of west Belfast in May 1981.
He said: “We are being told the people who are involved in the trouble are young people.
“If they are teens why are we firing plastic bullets at them? We have already lost enough lives and it does not matter whose life is lost.
“What are they going to do if some kid is killed by a plastic bullet. It will not make the situation better, we don’t agree with them being fired at anybody.”
Patrick Corrigan of Amnesty International said “the public disorder of the last few days has brought serious risks to life and limb, and the police must be able to carry out their duty to protect the public”.
“It is an unenviable task, and it is distressing to hear that officers have already been injured in the line of duty,” he said.
He also raised concerns about the use of force by police.
“Police use of plastic bullets and water cannons is always a worrying development, particularly if deployed where children are present,” he said.
“AEPs have the potential to cause serious injury and even death, particularly to children, a risk highlighted by the PSNI’s own guidance.
“With so many children on the streets, and the risk of serious injury via direct hit or ricochet, there is a significant risk in their use in current circumstances.”
Mr Corrigan said that under the law “the use of force by the police must be both necessary and proportionate and all such uses of force will require investigation by the Police Ombudsman for Northern Ireland”.
The PSNI was contacted.
