Footage sent to the ABC appears to show two men attempting to hang themselves before being stopped by others, the broadcaster has reported.
Two others have reportedly swallowed razor blades, though these claims from advocates have not been verified.
The self-harm coincides with the transfer of two asylum seekers to a purpose built transit centre, more than a week after protests began against the transfers.
The temporary housing, built by the Australian Government near the provincial capital Lorengau, has raised concerns over safety and lack of security for asylum seekers in the Papua New Guinea facility.
Authorities in PNG confirmed the transfer of an Iranian man and a Pakistani man on Wednesday.
Approximately 50 further asylum seekers are expected to be transferred, while there are reports from advocates that as many as 58 detainees are being held in jail.
Protests in New York, Australia
Protests have been held in solidarity in Australian capitals, as well as New York, as the detainees at Manus Island enter the ninth day of action.
Rallies were held in Sydney, Melbourne and Brisbane on Wednesday and a further protest is scheduled to take place in Canberra on Thursday.
In an email from New York, filmmaker Alex Kelly said Australian expats gathered for a candle light vigil outside the Australian Consulate.
“We are opposed to these offshore detention centres, we want detainees to know there are many Australians and people around the world who support their struggle,” she said.
* Readers seeking support and information about suicide prevention can contact Lifeline on 13 11 14 or Suicide Call Back Service on 1300 659 467.
