Roughly 600 refugees and asylum seekers barricaded inside the centre have run out of food, water and medication, but are adamant it's safer to remain than risk being attacked by locals at the new accommodation facilities on the island.
The Australian government has not responded to Colville's comments. Its government has said the camp had been ruled illegal by PNG authorities and it had committed to supply other sites for 12 months.
United Nations rights spokesman Rupert Colville told a news conference in Geneva on Friday about the "unfolding humanitarian emergency" in the Manus island center, where asylum seekers have been reportedly digging wells to try to find water. They include Rohingya Muslims from Myanmar, Afghans, Iranians, Sri Lankans and other nationalities, and are nearly entirely men.
The relocation of the men is designed as a temporary measure, allowing the United States time to complete vetting of asylum seekers as part of a refugee swap deal, agreed on a year ago, under which Australia will accept refugees from Central America.
Service providers and contractors have left the island, according to Australian media reports.
Her Australian counterpart, Malcolm Turnbull, however said Canberra preferred to work through an existing refugee swap deal he negotiated with former U.S. President Barack Obama previous year.
The alternative accommodation being proposed is not finished or adequate to meet their needs, including security, he said.
Urging the governments of Australia and Papua New Guinea to fully respect their human rights, Colville said: "We repeat our overall concerns about Australia's offshore processing centers, which are unsustainable, inhumane and contrary to its human rights obligations".
Refugees at the detention centre had told The New Daily ahead of the meeting between the two leaders that New Zealand was their best hope of resettlement.
"At the moment hundreds of naked men are lying around me", Boochani wrote. "They force us to starve".
Ms Ardern has reiterated the NZ offer, first made under John Key's centre-right National government to Australia's previous Labor government in 2013.
"While [Australia] is not accepting refugees from Manus they have no right to reject New Zealand's offer".
It was extended by his New Zealand counterpart Jacinda Ardern when the pair met in Sydney on Sunday.
"We want our offer to remain on the table so we can assist as much as we are able in expediting a resolution on this issue", she said. "You can't keep political hostages".
Mr Turnbull will meet Donald Trump on the sidelines of the East Asia summit in the Philippines later this month and is facing calls to lobby for the U.S. president to speed up the resettlement process.