More than 2,000 incidents, including sexual abuse, assault and attempted self-harm, were reported over two years at an Australian prison for asylum seekers in Nauru, more than half involving children, the Guardian has reported.

Leaked documents published by the Guardian Australia on Wednesday detailed the level of abuse at the prison on tiny Nauru, one of two run by Australia on neighbouring South Pacific islands, and showed that children bore the brunt of the trauma.

The closely protected prisons, and Australia's tough immigration policy against irregular boat arrivals, have been widely criticised by the United Nations and human rights groups.

Under the policy, asylum seekers intercepted at sea are sent to Nauru and another prison on Manus Island, in Papua New Guinea, and told they will never be settled in Australia.

READ MORE: Refugee sets herself on fire at Australia's Nauru camp

The number of refugees and asylum seekers trying to reach Australia is tiny compared with Europe, but immigration has long been an emotive issue in the country and the policy has bipartisan political support.

Australia said it was seeking to confirm that all reports had been dealt with by Nauru police.

Following the claims, the UNHCR renewed a call to remove all refugees and asylum seekers from the prison.

"Although UNHCR is not able to verify the individual incidents raised by the reports, the documents released are broadly consistent with UNHCR’s longstanding and continuing concerns regarding mental health, as well as overall conditions for refugees and asylum-seekers on Nauru."

Refugees considering suicide

"It's important to note many of these incident reports reflect unconfirmed allegations," a spokeswoman for Australia's Department of Immigration said.

The more than 2,000 leaked incident reports published by the Guardian covered the period between August 2013 and October 2015.

Children account for less than 20 percent of the roughly 500 detainees held on Nauru. There were 59 reports of assaults on children in the period, and seven reports of sexual assaults. Some of the reports alleged abuse by guards against children, and there were other reports of sexual advances by unknown men.

READ MORE: 'At Nauru's detention centre, many of us think of suicide'

The reports showed there were 30 incidents of self-harm by children and 159 of threatened self-harm involving minors.

The remaining reports involving children covered a variety of issues, ranging from accidents to misbehaviour. 

One of the leaked incident reports said that a child had "written in her book that she was tired, doesn't like the camp and wants to die." The child wrote: "I want death, I need death".

Human rights groups said the leaked reports highlighted an urgent need to end Australia's offshore detention policy and that asylum seekers must be given medical and psychological support.

"It is clear from these documents, and our own research, that many have been driven to the brink of physical or mental breakdown by their treatment on Nauru," said Anna Neistat, senior director for research at Amnesty International.

Human Rights Watch and Amnesty investigated abuse at Nauru earlier in August. Their findings are available online.

In an interview with Al Jazeera, Amnesty's Graham Thom said: "We need to see a Royal Commission into these abuses occurring on Nauru, we need to see action. really ... They [the refugees and asylum seekers] should be brought back to Australia immediately."

Report: Severe abuse of Australia’s asylum seekers in Nauru

Source: Al Jazeera and agencies