It's alleged an Iranian boy was raped by an older male multiple times on Nauru and his mother threatened with harm if she reported the abuse.
A child asylum seeker who was allegedly raped three times while on Nauru is suing the Commonwealth government and detention centre operators.
The Iranian boy arrived in Australia by boat with his mother and was transferred to Nauru in October 2013, where he was allegedly raped three times by an older male over six weeks the following year.
Lawyers for the Iranian boy, who was 10 at the time, say the alleged repeated abuse shows a failure of duty of care.
According to the lawsuit filed by Maurice Blackburn on behalf of the boy, he suffers from post-traumatic stress, has suicidal tendencies and has self-harmed.
"He has difficulty eating, sleeping and experiences disturbing nightmares," Maurice Blackburn principal lawyer Dimi Ioannou told SBS News.
"He has been diagnosed with post-traumatic stress disorder as a result of this trauma that has occurred to him."
Ms Ioannou said she is concerned about how authorities handled the case after the abuse was reported.
"The importance of this case is that it is testing the law about protecting these people who are detained on Nauru.
"The fact that the Commonwealth, Broad Spectrum and Wilson owe this little boy a duty of care and failed to provide that. They failed to provide him with a safe environment."
The boy and his mother were flown off Nauru to Australia in October 2014 after the third alleged assault.
Ms Ioannou said authorities had been too slow to act.
"It [the alleged rape] happened on three different occasions. And the boy and his mother were not airlifted to Australia until after the third incident. The authorities and personnel did not act fast enough in this case."
More cases of alleged sexual assault on Nauru
The claim is seeking damages, including aggravated damages, interest and costs from each of the three defendants.
The lawsuit also accuses detention centre contractors Wilson Security and Broadspectrum, then known as Transfield Services, of lacking proper systems to monitor and protect detainees.
Wilson and the government have declined to comment as the case is before the court.
It is the latest legal case arising from offshore detention.
"This is just one of a number of cases we know of involving the alleged sexual assault of an asylum seeker on Nauru," Ms Ioannou said.
"People in detention, particularly children, are very vulnerable and you have to ensure a safe environment. In our view that did not occur in this case."
Earlier this month, an Iranian family were awarded at least $100,000 because of "traumatic experiences" while in detention centres.
Two lawsuits on behalf of 1,200 asylum seekers transferred to Manus Island and Nauru were also launched in December in the High Court.
Prime Minister Scott Morrison said earlier this month that more than 100 children had been taken off Nauru in the past three months with less than 10 remaining.
The government has said it is aiming to remove all asylum seeker children from the island by the end of the year.