An Iranian asylum seeker is in a critical condition after setting himself alight in protest in front of visiting United Nations officials on Nauru.
The 23-year-old was due to be medically evacuated after the incident on Tuesday.
"His outlook is not good at all," said Australian Immigration Minister Peter Dutton.
Three staff from the UN's refugee agency, UNHCR, were visiting Nauru at the time and witnessed the incident.
The man's actions were described as a "political protest" by the Nauruan government and have prompted further calls for the detention centre to close.
The incident came as the Papua New Guinea government announced it would close a detention centre on Manus Island, west of Nauru, after a court found it was unconstitutional.
"It's now time for Prime Minister [Malcolm] Turnbull to stand up and to shut down Nauru as well," said Australian Greens senator Sarah Hanson-Young.
Mr Dutton said confirmed there had been other self-harm incidents at Nauru, but was clear that anyone brought to Australia for medical treatment would be returned to Nauru.
"We have returned three people back to Nauru from Australia and they have returned because the medical assistance that they sought in Australia has been provided."