Seven people were arrested overnight on Tuesday and into the early hours of Wednesday morning, bringing the total for the five days to 62.
As well as the 12-year-old, two others were also children - aged 14 and 15.
"One of those arrests last night was of a 12-year-old child and I would like us to stop and reflect for a moment on that detail," PSNI Assistant Chief Constable Will Kerr said.
"A 12-year-old child was arrested on the streets of Newtownabbey at 1am for being engaged in attacking police.
"Apart from how frighteningly irresponsible it is to allow a child of that age out on the streets at 1am, to allow them to engage in a riot - it just beggars belief."
These are children, and they are children who deserve protection and better from their communities and from their families.
ACC Will Kerr, PSNI
A total of 71 police officers, including 68 from the PSN and three brought in from Great Britain, have been injured while trying to restore order.
An extra 300 mutual aid officers from GB are now due to arrive in Northern Ireland, with 1,000 having previously been deployed - half of whom have since returned to their own bases.
On Tuesday night, the fifth consecutive night of violence, 35 petrol bombs were thrown and six cars were burned out.
The majority of the petrol bomb attacks happened at Templemore Avenue in east Belfast, after large crowds gathered in the Lower Newtownards Road area.
There were also pockets of disorder in the north of the city - including an attempt to hijack a bus on the Crumlin Road.
"The number of people involved in the disorder was lower than on previous nights," a PSNI statement said.
"Trouble began at approximately 10.30pm and continued sporadically for a few hours. Calm was restored across most areas by approximately 12.30am.
"Four cars were set alight in the Templemore Avenue area of east Belfast, a car was set alight in Mount Vernon, with a car and a moped set alight on the O'Neill Road in Newtownabbey."
The 15-year-old youth arrested overnight in Newtownabbey has since been charged with riotous behaviour in relation to the O'Neill Road disturbances. He is due to appear at Belfast Youth Court on Wednesday afternoon.
Also in Newtownabbey, a 36-year-old man has been charged with possession of petrol bombs. He is due before court in Belfast on Thursday.
Elsewhere, a 30-year-old man has been charged with riotous assembly, obstructing police and resisting arrest in connection with trouble in the New Lodge area of Belfast.
He will appear at Laganside Magistrates' Court on Thursday.
The disorder first broke out on Friday night, in response to a Parades Commission determination banning the Orange Order from marching their return Twelfth parade past the Ardoyne shops.
At least 125 petrol bombs have since been thrown and 51 baton rounds fired by police.
On Wednesday, Northern Ireland Secretary of State Theresa Villiers joined ACC Kerr to speak out against the intense violence.
"It is vital that we see calm return to the streets of Belfast," she said
"It's a huge concern that so many officers have been injured. The reality is it could so easily be a situation where we were talking about very serious injuries or even fatalities."
Those scenes are appalling for the communities concerned, hugely fraught with risk for the police and bad for Northern Ireland as a whole.
Secretary of State Theresa Villiers
In east Belfast, a group of paramilitary representatives, community leaders and local minsters have met to discuss the situation.
Gary Mason from the East Belfast Mission told UTV: "We condemn unreservedly violence and wish to see it end immediately.
"It has a negative impact on our community and relations more generally."
DUP councillor Gavin Robinson added that calls were being made for an end to the violence, but not to the protests.
"Because I think we not only acknowledge that people will want to protest and do have genuine frustrations and anger, but we also acknowledge that is their democratic right," he explained.
"But they have to do it lawfully."
According to Sinn Féin's Niall Ó Donnghaile, the process was useful.
"Because any meeting to bring people together, any meeting that cuts through rumours and myths and some of the dangerous rumours on social meda, is useful and very, very helpful to reassure residents - particularly at the interfaces," he said.
It comes after politicians were recalled to Stormont on Tuesday to debate the recent trouble.
A motion put forward by the Democratic Unionist Party, which criticised the Parades Commission's determination on the Twelfth of July, was passed by 43 votes to 42.
DUP leader Mr Robinson told the special sitting: "I do not think that anybody who takes a ceremonial sword to the head of a police officer can honestly find anywhere more suitable to be than in prison.
"There is no excuse for anybody carrying out what was an attempt to murder or at least to seriously injure a police officer."
But petrol bombs and masonry were thrown at police during Tuesday night's disorder in east Belfast which lasted for over two hours, although there were no reports of any injuries.
Disorder in north Belfast broke out following a white line protest in the Mount Vernon area.
Police were attacked with petrol bombs and a car was set alight. A hijack attempt was made on a bus in the Crumlin Road area and youths placed items on North Queen Street and set them on fire, while petrol bombs and other missiles were thrown.
There was also disorder on the Woodvale Road and a police vehicle was petrol bombed earlier in the evening on the Whitewell Road.
At least one petrol bomb was thrown in the Blacks Road area of south Belfast and at least one paint bomb was thrown in the Kingsway area.
Outside of Belfast, a car and moped were set alight in Newtownabbey during disorder which started at 11.15pm and ended at around 1.40am. Police were attacked with masonry and paint bombs and two petrol bombs were thrown at a police vehicle.
Opposing factions also gathered in the Corcrain Road area of Portadown.
Police said: "A number of fireworks were let off by the crowd and a number of golf balls were thrown, however there was no serious disorder."