The Refugee Action Coalition says Australia needs to take responsibility for the safety of unaccompanied minors seeking asylum and living on Nauru.
Its spokesperson, Ian Rintoul, says there are 29 asylum seekers under the age of 17 living in special housing, away from the Australian-run detention centre.
Mr Rintoul says last month, a group of Nauru locals assaulted a 17-year-old Iranian at the detention centre, and then went on to assault four Afghanis living in housing set aside for unaccompanied minors.
He says Australia has an obligation to look after them.
"There's no services whatsoever for them. Save the Children has overall responsibility but there's no services, there's no education, even just basic things to fill their time - classes of any kind, activities of any kind, planned excursions, they're effectively left to their own devices."
Ian Rintoul says Nauru police have shown a complete disinterest in following up the complaints.
The Nauru government, however, has condemned the attack as racist and opportunistic, and says it will not tolerate any such violence.