Australians have rallied against the alleged mistreatment of young people in detention, including the hooding and physical restraint of teenagers, amid calls for an inquiry into the abuse to be expanded.

Earlier this week, Australian television aired graphic footage showing six Aboriginal boys being stripped naked, tear-gassed, held in solitary confinement and shackled to a chair as a restraint measure.

The video shocked the country and prompted Prime Minister Malcolm Turnbull to order a royal commission into how youths were treated at the Don Dale Centre in the Northern Territory in 2014 and 2015.

But at snap "emergency protests" in Sydney, Melbourne and elsewhere on Saturday, hundreds gathered to show their outrage at the mistreatment of the boys.

CCTV footage from the Don Dale Youth Detention Centre shows a boy hooded and strapped to a mechanical chair  [EPA]

"If we could see some action, some real fair and just action taken, I think that would allay some concern," Sydney community elder Aunty Jenny Munro told the Australian Broadcasting Corporation.

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But there have been calls for the royal commission to be expanded beyond the Northern Territory, given concerns about physical and emotional abuse in youth detention centres in other states.

Opposition Labor leader Bill Shorten said his party fully supported the inquiry but argued that it should also have indigenous commissioners.

"This royal commission has to be with Aboriginal people, not to Aboriginal people," he told reporters in the northern city of Darwin.

"I believe it would be appropriate for the royal commission to have two co-commissioners who are Aboriginal Australians, strong people, men and women, who can make sure the voices and the experiences of Aboriginal Australians are given full justice in this royal commission."

Indigenous young people aged 10-17 were 17 times as likely to be under Australia's youth justice supervision, according to data gathered by the Reuters news agency. They were also 28 times as likely to be detained.

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Nigel Scullion, Australia's minister for indigenous affairs, has since apologised for not being aware of the what went on at the Don Dale centre. 

One barrister described the treatment of some teenagers at the facility as reminiscent of Guantanamo Bay, the notorious US military prison in Cuba. 

"I'm sorry I wasn't aware of the full circumstances that were exposed this week," Scullion said.

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Source: Agencies