The Department of Immigration would not say how many were involved because the number kept fluctuating.

Reports from Nauru say an Iranian man has been on a hunger strike for 22 days. An Immigration spokesman would not confirm this for ''operational'' reasons but said no one had yet been taken to Nauru's hospital.

An asylum seeker on Nauru, who asked not to be named, said that the environment was ''like a mental hospital''. ''These guys were OK but this environment [is] making them mental, making them crazy,'' he said.

The man said asylum seekers continued to ask officials when their claims for refugee status would be processed but officials were unable to tell them.

''This camp, I think, this is not suitable for anyone,'' he said. ''We are humans. I don't think that an animal can survive this.''

A group of asylum seekers has set up a Facebook page to reach out to the Australian public.

They wrote: ''As a human being in this critical condition, we are not being given the fair treatment, which affect us physically and mentally … In our homeland we were in a danger of being tortured physically but here we are facing mental tortured which are effecting us mentally.''

Amnesty International's refugee campaign co-ordinator, Alex Pagliaro, said the links between long-term detention and deteriorating mental health were well established. ''It is increasingly worrying, what is happening on Nauru, and that things seem to have deteriorated so fast,'' she said.

The Immigration Minister, Chris Bowen, said 26 Sri Lankans who had arrived in Australia over the past week were sent home on Friday after failing to make any claims for protection.