A United Nations anti-torture inquiry in Geneva has grilled Australia over living conditions in its detention centres in Nauru and Manus Island.

On Monday night, the UN Committee against Torture began reviewing Australia’s record as a convention signatory for the first time since 2008.

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Chairman Claudio Grossman raised questions about the controversial detention centres, requesting specific details about the layout of the centres before asking for a copy of the guards’ training manual.

“They are actually in a place surrounded by fences? And you need a guard to move from one place to the other?” Mr Grossman asked.

He also raised concerns over the length of processing times for refugee claims, with the average wait being 10 months in Nauru and two years in Papua New Guinea.

“That would produce tremendous anxiety in people,” Mr Grossman argued. “I can’t imagine the number of people that are there and don’t know where they are or what is happening.”

Conditions in the offshore processing centres have previously been described as “inhumane” by both Amnesty International and the United Nations High Commissioner for Refugees.

The UN committee is set to hand down its report card on November 28.

— with AAP