Australian immigration minister Tony Burke Wednesday described as "horrific" explosive claims that asylum-seekers at one of its processing camps in Papua New Guinea are being raped and tortured.
A former senior official at the Manus Island facility also detailed "almost daily" self-harm and attempted suicides while warning weapons were being accumulated in readiness for a break-out attempt.
"I've never seen human beings so destitute, so helpless and so hopeless before," Rod St George, the former head of occupational health and safety at the centre, told SBS television.
"I took the position with every intention of making the place a safer environment but it proved quite rapidly to be an impossibility."
Disgusted by what he saw, St George quit.
His allegations come just days after Australian Prime Minister Kevin Rudd announced that the facility would be massively expanded as part of a new hardline plan to send all asylum-seeker arrivals to Papua New Guinea.
Under the policy, unauthorised boatpeople arriving in Australian waters will now be banished to Manus Island and elsewhere in the Pacific nation for assessment and even if found to be "genuine refugees" they will have no chance of being settled in Australia.
Instead, they will have to remain in poverty-stricken PNG, be sent back home or to third countries.
St George, a former prison guard, said up to half a dozen young men were assaulted and raped by fellow inmates, while others were beaten and forced to sew their lips together to protest over conditions.
The men who were sexually assaulted were sent back to the same tents as the people who raped them, he claimed.
"There was nothing that could be done for these young men who were considered vulnerable, which in many cases is just a euphemism for men who are being raped," he said.
"They had to stay where they were."
He added that one man had his eardrum perforated when he had solvent poured into his ear, and criticised immigration department officials at camp for their handling of the cases.
Burke said he would fly to Manus Island this week to investigate.
"I'll be in Manus in the next couple of days and I'll have a look for myself," he told ABC radio, adding that he was made aware of the allegations a week-and-a-half ago but only spoke to St George on Tuesday evening.
"The allegations were horrific. I wish I'd had an opportunity to get the specifics of them earlier than last night because I would've started acting on them earlier than last night," Burke said.
"There's no doubt that what has been described involves some situations and crimes which must not be allowed to occur."
Australia has struggled to stem an influx of asylum-seekers arriving by boat, with record numbers turning up in 2012 and more than 15,600 so far in 2013.
Hundreds have drowned making the journey, with another boat sinking off Indonesia late Tuesday with casualties feared.