An Iranian asylum seeker being held on Nauru is in a critical condition after setting himself alight, the Nauru government says.
It said the 23-year-old was carrying out a political protest, to coincide with a visit by representatives from UN refugee agency UNHCR.
The man is among hundreds of asylum seekers and refugees held on the island by Australia, many of whom have been held for three years.
In a statement, the government said it had requested that the injured man be flown to Australia for treatment.
It said it was premature to speculate on the details of the incident, but a full investigation was being carried out.
Such protests happened during high-profile visits because some within the refugee community were trying to influence the Australian government's offshore processing policies, it added.
The Australian Refugee Action Coalition said five asylum seekers had attempted self-harm in the past 24 hours.
It said, as well as the man who tried to self-immolate, four people drank washing powder last night following 38 days of protest at the family camp for detainees.
Coalition spokesperson Ian Rintoul said there were also fears for two Iranian women - Marziyeh Faghih, 28, and Amineh Shajira, 34 - who had been missing from Nauru since Sunday.
"The family has been beside themselves. They've pleaded with the police, they've pleaded with case officers, but no proper search has been mounted."
Mr Rintoul said family members of the missing women said the pair had talked previously about taking a boat and sailing themselves off the island.
The Nauru government said it believed its system for those seeking asylum was world-class.
Access to Nauru is heavily restricted, with media representatives required to pay $US5000 as a non-refundable visa application fee.