An interpreter working for the Australian Immigration Department claims Papua New Guineans employed by security guards at the Manus Island detention centre attacked asylum seekers with machetes, knives and rocks on Monday night.
An Iranian man was killed and at 70 asylum seekers injured.
The Sydney Morning Herald reports Azita Bokan alleges asylum seekers used plastic chairs as shields when they were attacked by locals who entered the centre.
This incident followed days of violence at the centre.
Ms Bokan says she saw people who had suffered 'massive head injuries.
She says she had not witnessed the violence, but was in the area where the injured were taken, and was told injuries were caused by machetes, knives, rocks and table legs.
Ms Bokan says there was blood everywhere and the number injured was horrific, with at least one with a slashed throat.
Ms Bokan, who had been on Manus for a week, claims the unrest on Sunday was sparked when the detainees were pressured to voluntarily return to their homelands and told there was no prospect of resettlement in Australia, a third country or on Manus.