According to the notice, refugees would be provided with support including residential accommodation
Amnesty International welcomed the development, but expressed concerns about the men's safety
Those still living at the detention centre have received the news with suspicion, according to one refugee
Papua New Guinea's Government has offered refugees living at the Manus Island detention centre the opportunity to voluntarily transfer to Port Moresby.
According to a notification from the Immigration and Citizenship Authority of Papua New Guinea, sent to the ABC by a Manus refugee, those who accept the offer will not be subject to immigration detention.
The notice said they will be provided with residential accommodation, one-off financial relocation support, a weekly living allowance, health services and employment support.
Human rights lawyer David Manne said while voluntary relocation was a "preferable short-term solution", it was not a resettlement offer and would not end "the cruel limbo they've suffered for the last six years".
"These refugees are not being provided with any assurance that they will be able to be taken to safety where they can rebuild their lives in the future," he said.
Amnesty International Australia's Refugee Coordinator Dr Graham Thom commended the PNG Government for making the offer.
"It is great news that these men, who have been trapped on Manus for six years are being offered the chance to escape their island prison and settle in Port Moresby," Mr Thom said in a statement.
"It is vital that there is a long-term plan for these refugees and that their rights are protected."
Mr Thom also emphasised the need to address the "ongoing psychological and health issues" of refugees who have been living under conditions he described as "deeply inhumane and degrading".
'They want to keep us in limbo'
Those still living at the detention centre have received the news with suspicion, according to Manus refugee Behrouz Boochani.
"Yesterday they came here and announced they are going to close Manus prison camp and transfer at least 120 people," said Mr Boochani, who has written about the situation for detainees.
"We don't know what will happen with us. We don't know what is their plan."
Mr Boochani told the ABC that although they suspected the move was no more than a continuation of "the political game", they would be forced to accept the offer.
But he said permanent settlement in Port Moresby was not possible and would mean they could never see their families, who they have been separated from for six years.
"Australian people — immigration officers — are living in Port Moresby under high security. They know better than us that we cannot start a new life in this country. It is impossible for us," he said.
"They want to continue to keep us in limbo."
Mr Manne urged the Australian Government to reconsider resettlement offers made by New Zealand.
"It is critical that the Australian Government look more broadly at other options," he said.
They're people that have a well-founded fear of being persecuted if they were returned to their home country.
"They are people in need of protection, and people who deserve to have, in the future, a safe and secure place to live."
Mr Thom said greater clarity about their legal status and how it might impact their ability to settle elsewhere was also needed.
"The Australian Government cannot wash their hands of responsibility for them once they have relocated," he said.
"They put them on Manus, and they are responsible for ensuring they are suitably resettled, including bringing them to Australia where appropriate."