SYDNEY • Australian Prime Minister Malcolm Turnbull has ordered an inquiry into the treatment of children in detention after the airing of a video showing prison guards tear gassing teenage inmates and strapping a half-naked, hooded boy to a chair.

"Like all Australians, I've been deeply shocked - shocked and appalled by the images of mistreatment of children," Mr Turnbull said on Australian Broadcasting Corporation (ABC) radio yesterday as he announced a Royal Commission, Australia's most powerful, state- sanctioned inquiry. "We're going to move swiftly and decisively to get to the bottom of this."

ABC aired security footage on Monday of inmates in a Northern Territory juvenile detention centre also being stripped naked, carried by the neck and thrown onto a mattress in a cell, and held for long periods in solitary confinement.

The footage from the Don Dale Youth Detention Centre in Darwin, shot between 2010 and 2014, showed guards mocking inmates and covering a teenager's head with a hood and shackling him to a chair with neck, arm, leg and foot restraints.

Barrister John Lawrence told ABC the teen's treatment was reminiscent of Guantanamo Bay, the United States military prison in Cuba that holds terror suspects.

"We are talking about kids that are being shackled with handcuffs on their ankles, their wrists, their waist areas. They are being shackled to chairs," said Mr Lawrence, the former president of the Northern Territory Bar Association.

"One of them has had the experience of sitting in one for just under two hours with a spit hood over his head, a la Guantanamo Bay."

Northern Territory Chief Minister Adam Giles sacked his corrections minister within hours of the broadcast, taking over the portfolio himself, and said that information about the abuse had been withheld from him.

"I predict this has gone on for a very long time," he said, ordering the police to investigate whether any laws had been broken by the prison guards.

Lawyer Peter O'Brien, who represents two of the abused boys, said he was suing the state on their behalf, alleging assault, battery and false imprisonment.

"It seems as if this abuse is built into the very core of the system," he said in a statement.

The video also raised the issue of the treatment of Aborigines, who make up 94 per cent of juvenile inmates in the territory.

An emotional Aboriginal and Torres Strait Islander Social Justice Commissioner Mick Gooda told reporters: "Our (indigenous) people have known about things like this... and to just see it laid bare in front of us last night must be a wake-up call to everyone in Australia - that something's got to be done about the way we lock our people up in this country."

The New South Wales Aboriginal Land Council demanded the Royal Commission include all states and territories, as well as an examination of the over-representation of Aborigines in detention. Aborigines comprise just 3 per cent of Australia's population but make up 27 per cent of those in prison.

Australia's Human Rights Commission president Gillian Triggs said: "We have been reporting on this question of indigenous incarceration, particularly of juveniles, for many, many years and we have had many, many reports... on the appalling conditions in which they are held."

REUTERS, AGENCE FRANCE-PRESSE