Police in Belfast were forced to abandon a bid to dismantle a bonfire planned in the city last night following a stand off with republican youths.
Bricks and bottles were thrown and at least one police officer was knocked out ahead of the bonfire in the New Lodge area.
It marks the anniversary of the introduction of internment on this day back in 1971.
Police retreated from a confrontation over concerns innocent bystanders could be hurt, a senior commander has said.
Violence which left three police officers injured was probably orchestrated by dissident republicans, Police Service of Northern Ireland (PSNI) Assistant Chief Constable Alan Todd added.
He regretted the failure of an operation involving more than 150 officers to allow contractors to remove the wooden pallet pyre in the nationalist estate.
Young people climbed on top of the pile in triumph and the police operation ended with vehicles speeding from the estate under a hail of missiles.
The PSNI said six petrol bombs had been recovered and a 13-year-old youth has been arrested on suspicion of riotous and disorderly behaviour.
Mr Todd said: "It is a question for me as a police commander.
"Am I going to continue ramping up the use of police force against a wider community with innocent members present?
"Including water cannon, including the potential for AEPs, commonly known as plastic bullets in parlance in the area.
"Am I prepared to do that merely to save face on behalf of the organisation and sacrifice public safety as a result?
"The answer is, no I am not."
The withdrawal followed a stand-off with republican youths over the bonfire marking the introduction of internment without trial during the Troubles. Missiles and metal fencing were hurled at officers.
Police moved in early on Thursday to facilitate contractors tasked with removing the structure.
The officers were injured during sporadic bouts of violence.
The estate was later barricaded using metal fencing following the police retreat.
The bonfire was built on land owned by Northern Ireland's Department for Infrastructure.
The Housing Executive urged residents to leave the nearby Oisin and Fianna tower blocks as they cannot guarantee their safety, due to the proximity of the blaze.
Referencing the murder of journalist Lyra McKee by dissident republicans in Derry earlier this year during disturbances, Mr Todd said police did "not need to learn the lesson" of the risk to innocent bystanders.
Mr Todd said a significant number of women and children in the crowd were being used as human shields.
The senior commander said he had an obligation to minimise the use of force and the risk to public safety.
"I regrettably have had to take a decision today that the risks of continuing the operation to remove a bonfire were outweighed by the risks that operation would then pose to the wider community, to women and children and others there present.
"That is a matter of regret to me that we were not successful in the objective of the operation but it is nonetheless a responsible, professional policing decision taken within the law and taken with very little room for other decisions to be made."
Mark Lindsay, chair of the Police Federation for Northern Ireland, said officers trying to protect the community and lawful agencies are once again caught in the middle and in the firing line.
"This behaviour is contrary to the overwhelming wishes of the people of New Lodge who do not want this bonfire or their area hijacked by young thugs."
Operation Demetrius in 1971 saw hundreds arrested across the region on suspicion of being involved with paramilitary groups.
The vast majority arrested were nationalists, although a significant number of them had no connection with the IRA.
The anniversary has traditionally been marked by many from the nationalist and republican tradition with bonfires, although recent years have seen a move away from pyres towards community-based diversionary activities.
