Australia's prime minister has ordered a sweeping investigation into claims that teenagers were abused at a juvenile detention centre in the country's north.
Malcolm Turnbull said he would launch the royal commission, Australia's highest form of inquiry, after graphic footage emerged of teenage detainees being tear-gassed and stripped naked.
In one instance, one of the teens was shackled to a restraint chair with a hood placed over his head before being left alone for hours.
The footage, shown on the Australian Broadcasting Corporation's investigative programme Four Corners yesterday, was filmed largely at a youth detention centre in the Northern Territory city of Darwin between 2010 and 2015.
"Like all Australians, we have been deeply shocked - shocked and appalled - by the images of mistreatment of children," Mr Turnbull told Australian Broadcasting Corporation radio.
"We will get to the bottom of what happened here."
Human rights activists accused the government of ignoring the issue until it became public because the teenagers involved were indigenous.
The Northern Territory has the highest rate of youth detention in the country, and 97% of detainees are Aboriginal.
"Amnesty International has repeatedly raised concerns of abuse of children being held in youth detention centres in the Northern Territory," Julian Cleary, indigenous rights campaigner at Amnesty International Australia, said.
"As this programme shows, these are not isolated incidents. The (Northern Territory) government has failed to deal with systemic issues with the treatment of children in its youth detention system."
When the tear gas incident occurred in 2014, officials said guards had used the chemical to subdue six teenagers who had staged a riot.
But CCTV and video footage filmed by staff at the centre appears to show that the tear gas was used after just one youth escaped from his cell, while the other five remained locked in their cells.
The guards are heard laughing as the teens cough and cry after multiple shots of tear gas were fired into the isolation wing where they were housed. One of the detainees can be heard saying he cannot breathe.
In another video, a guard is seen picking up a 13-year-old boy and hurling him across the room on to his bed.
The same boy is also seen in footage from a different Northern Territory detention centre being stripped naked and held face-down on his bed by three guards after he apparently threatened to hurt himself.
Northern Territory chief minister Adam Giles said he had never seen the footage before it last night and blamed a "culture of cover-up" within the corrections system for the government's lack of action until now.
"I sat and watched the footage and recognised horror through my eyes," Mr Giles told reporters in Darwin.
Mr Giles said he had removed Northern Territory corrections minister John Elferink from his position in the wake of the scandal.
The royal commission is expected to begin holding hearings as early as September, with a final report due to be released early next year, Mr Giles said.
Indigenous affairs minister Nigel Scullion said the footage was particularly shocking because the guards involved appeared cavalier about their actions.
He said the officers should face criminal charges.
"They knew ... that their behaviour was clearly not right, it was evil, but they also knew they had absolutely no chance of that being a problem to anyone," he said in Canberra, the capital.
"Such was the culture of cover-up, such was the culture of brutality."