Govt offers to move PNG refugees to Nauru

Under Canberra's harsh immigration policy, asylum-seekers who try to reach Australia by boat are barred from entering the country and are instead sent to remote Pacific camps pending eventual resettlement elsewhere.

Conditions in the camps have been widely criticised by refugee advocates and medical professionals, with reports of widespread abuse, self-harm and mental health problems.

A PNG court ruled last year that holding people on Manus was unconstitutional and the camp is now set to close by the end of October, with Canberra saying on Wednesday that refugees could move to Nauru instead.

"The government of Nauru has agreed to receive PNG-determined refugees in Nauru to await third country resettlement," a spokesman for Australia's Immigration Minister Peter Dutton said in a statement.

"Relocation is voluntary; no one will be forced to move to Nauru."

The detainees face an October 23 deadline to express their interest in moving to Nauru.

Canberra also struck a deal with former president Barack Obama for the United States to resettle an unspecified number of refugees from Manus and Nauru, but the agreement has been harshly criticised by his successor, Donald Trump.

A first batch of 54 refugees from Manus were notified of their acceptance to the US in late September, with 24 flying out to America a few days later.

But hundreds more remain at the camp, with some expressing fears that a transfer to Nauru could further prolong their agony.

"Sending refugees from Manus prison camp to Nauru is unacceptable," tweeted one Manus detainee, Behrouz Boochani.

"How can the gov want to send people from hell to another hell after 4yrs?"

Daniel Webb from the Human Rights Law Centre, which has challenged offshore detention in court, called on the government to transfer the refugees to Australia instead.

"If (Australian Prime Minister) Malcolm Turnbull honestly believes that people will eventually go to the US -- fine. But in the meantime he should bring them here to safety in Australia," Webb said in a statement.

"If Malcolm Turnbull leaves people in danger any longer, then further misery, suffering and death is absolutely inevitable."

Some 371 men, women and children are being held at Nauru, with a further 791 on Manus, according to immigration department figures as of July 31.