"We call on the Australian government. who interned the men in the first place to immediately provide protection, food, water and other basic services", United Nations rights spokesperson Rupert Colville told a news briefing.

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.

Peter Dutton says the refugees should move to alternative accomodation.

"That is an offer that does remain on the table, so whilst it has not been taken up immediately, the prime minister thanked New Zealand for the offer, acknowledged it and it is something that still remains in place", she said.

"The Australian government is not honest".

Ms Ardern said on Sunday she understood the Turnbull government had prioritised the U.S. agreement, but described her own offer as "genuine". "We will not have our immigration program, our sovereignty, our borders, outsourced to people-smugglers", he said.

For four years, Australia has paid Papua New Guinea, its nearest neighbour, and Nauru to house asylum seekers who attempt to reach the Australian coast by boat.

Ms Ardern offered to accept 150 refugees from the offshore detention camps, similar to an offer made by former NZ Prime Minister John Key in 2013. They include Rohingya Muslims from Myanmar, Afghans, Iranians, Sri Lankans and other nationalities, and are nearly entirely men.

"We repeat our overall concerns about Australian offshore processing centres which are unsustainable, inhumane and contradictory to its human rights obligations", Colville said. "They are starving and their bodies are getting weak".

"I acknowledge that, while New Zealand has not had to contend with these issues on our shores, it's hard to ignore the human face of this situation and nor should it be ignored", wrote Ardern.

The government has been facing growing pressure to accept the offer in recent days, with Opposition Leader Bill Shorten saying on Friday that Mr Turnbull should honour New Zealand's proposal and Liberal MP Kevin Andrews breaking ranks to join that call on Sunday. "You can't keep political hostages".

However, during a bilateral meeting in Sydney with his counterpart Jacinda Ardern on Sunday, Mr Turnbull said his government was focused on a United States resettlement deal to take up to 1250 people.

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 USA president to speed up the resettlement process.