Amnesty International fears it's only a matter of time before there's a fatality on Manus Island, as the detention centre prepares to close and some refugees are left behind.
The human rights group called on immigration department officials at a Senate estimates hearing in Canberra on Monday to spell out what plan B is for those in Papua New Guinea and Nauru who are not settled in the US.
"Another tragedy is on the horizon, it's coming... it's coming the way of those men and they know it and that's why they are so fearful," Amnesty spokesman Graham Thom told reporters in Canberra on Monday.
"People will die if you keep them in those camps and on those islands."
Amnesty, the Refugee Council and the Human Rights Law Centre have joined forces to argue refugees not resettled in the US should be brought to Australia.
Asked about the prospect of the PNG-base refugees being sent to Nauru, Refugee Council spokesman Tim O'Connor said they don't deserve to be bounced from island to island.
The PNG detention centre is slated for closure in October but officials have warned demolition will start within weeks.
Immigration Minister Peter Dutton has previously said refugees who aren't taken under the US resettlement deal may settle in PNG, while roughly 400 non-refugees will be sent back to their home country.
Refugees supporters seized on the Good Friday shooting in which navy officers opened fire on the detention centre with automatic weapons, to bolster their argument PNG was not safe.
