It also slammed the island nation's "limited capacity" to investigate allegations of sexual assault of children and its failure to follow up complaints, and severely criticised the harsh living conditions inside Australian's regional processing centres.

Among the global body's concerns were a lack of clean drinking water and poor sanitation, the absence of a dedicated paediatrician and the reported use of illegal corporal punishment against children at the camps.

The UN's Committee on the Rights of the Child also found that Nauru has made no progress towards honouring a promise made last year to establish a human rights watchdog.

The report identified "inhuman and degrading treatment, including physical, psychological and sexual abuse, against asylum seeking and refugee children", citing last year's independent review by former Commonwealth integrity commissioner Philip Moss.

It comes as the Turnbull government comes under increasing pressure to remove asylum seekers and refugees from Nauru and Manus Island or face the "high likelihood" that many more will attempt suicide.

The UN concluded that mental ill-health, including "feelings of hopeless and often suicidal ideation", was exacerbated by prolonged uncertainty and poor living conditions inside the hot, humid camps.

Recovery options for traumatised children were systemically poor in Nauru, the UN suggested. It slammed the lack of assistance for "physical and mental recovery" of children who experienced trauma before arriving in Nauru and then spent long periods languishing in detention.

There were 410 people in Australian immigration detention in Nauru at the end of August: 306 men, 55 women and 49 children, according to the Department of Immigration and Border Protection.

While the government insists that none of those on Nauru or Manus will come to Australia, Fairfax Media believes it has made progress towards finding a third country option, with the US being a possibility.

Well-placed sources say an announcement on third-country options is not imminent, but that much work is being done and that Prime Minister Malcolm Turnbull is determined that the issue be resolved.

The CRC issued its report based on hearings in Geneva, meetings with civil society groups, Nauru's own submissions and a review of previously published literature.

The committee urged Nauru - and by extension, Australia - to immediately remove asylum-seeking children and their families from the RPCs, and find "permanent, sustainable resettlement options" for recognised refugees, including reasonable access to employment.

It also called on Nauru to ensure that staff working at the RPCs were adequately trained in the identification of vulnerable children and those at risk of self-harm, and to develop a system to ensure incidents of self-harm were referred to the appropriate powers and followed up.

In January, Fairfax Media revealed asylum seekers in detention on Nauru were committing acts of self-harm every two days, including swallowing insect repellent, bashing their heads against walls and dousing their bodies with boiling water.

The UN said it was also "gravely concerned" about reports that RPC detainees had their daily water intake rationed. Limited access to clean, safe drinking water and sanitation left children and families "vulnerable to dehydration and other serious health problems", the report said.

The committee slammed the lack of health services available for asylum-seeking and refugee children, and in particular noted the main medical provider at the RPCs did not have a paediatrician.

There was also evidence that children in detention, including Australia's RPCs, were still being subjected to corporal punishment despite the practice being prohibited in Nauruan schools and jails.

The report harshly condemned the iron curtain of secrecy surrounding the detention centres, which journalists and foreign organisations have found it extremely difficult to penetrate. Reports that "some international organisations have been subjected to intimidation" were of particular concern.

Last month, Paris Aristotle, the pre-eminent adviser on refugee issues to both sides of politics, urged the Turnbull government to move quickly to remove the asylum seekers from both Nauru and Manus.

Speaking in his capacity as head of the Victorian Foundation for Survivors of Torture, Mr Aristotle said: "If the governments involved don't take swift action to restore hope, we believe it is highly likely that many more men and women will express their despair by attempting to harm and kill themselves.

"We also hold grave concerns that children and young people in Nauru will respond in the same ways."

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