None of the 14 cases of sexual assault reported at the Manus Island immigration detention facility over the past 18 months have led to prosecutions, Senate estimates has heard.

Immigration staff told a Senate committee that over the period from March 24, 2014 to September 29, 2015, the regional processing centre recorded 14 sexual assaults, 213 physical assaults and 798 occurrences of abusive and/or aggressive behaviour.

The Manus Island facility houses single male adults.

There have also been multiple sexual assaults on Nauru, involving both asylum seekers and processed refugees.

Immigration spokeswoman Cheryl-Anne Moy told Senate estimates that there had been 10 reports of sexual assault involving children in immigration detention in the period between September 2013 and September 2015.

Ms Moy said five of those reported assaults related to a lone incident.

There were nine reported sexual assaults of adults in immigration detention on Nauru over the same period, as well as 82 allegations of physical abuse involving children.

Outside the centre, there have been 10 reports of sexual assault against processed refugees between May 2014 and September 2015.

Ms Moy said "a number" of the sexual assaults had been reported to Nauruan police.

Senate estimates also heard figures on self-harm by asylum seekers and refugees.

From January to August 2015, there were 74 reported incidents of self-harm on Nauru and 34 on Manus Island. There were also 23 and two threats of self-harm respectively.

Figures were also provided for the onshore detention network for the three months to September 2015, totalling 140 incidents and 189 threats.