More than 20 refugees living on Manus Island have self-harmed or attempted suicide since the federal election, according to refugees and advocates who say the situation is now "out of control".

Key points: 26 refugees have self-harmed since the election, according to refugees and advocates

26 refugees have self-harmed since the election, according to refugees and advocates Refugees believe they face another three years in offshore detention under the Coalition

Refugees believe they face another three years in offshore detention under the Coalition The local hospital on Manus Island is struggling to cope with the influx of cases

Advocate Ian Rintoul, who is in regular contact with refugees being held in offshore detention, told the ABC he had received reports of up to 23 incidents on Manus, including at least six in the past 24 hours.

Mr Rintoul said he was aware of at least three more cases in Port Moresby, where a number of refugees have been hospitalised.

"The situation was already deteriorating prior to the election, but subsequent to the election it is now out of control," he said.

"It's clear that the crisis situation is only going to spiral further."

Refugees have 'completely lost hope'

There are more than 500 men currently living on Manus Island, most of whom have been deemed refugees.

Refugee Behrouz Boochani has described the situation on Manus as "out of control". ( AAP: Jason Garman/ Amnesty International )

Kurdish-Iranian journalist Behrouz Boochani, who has been detained on Manus since 2013, also told the ABC that at least 26 refugees in Papua New Guinea have self-harmed or attempted suicide since the Coalition was re-elected on May 18.

"That negatively impacted on the refugees and people lost their hope, completely lost hope," he said, adding that many believe they face another three years in detention under the Coalition.

A bilateral Australia-United States deal to resettle 1,200 refugees from Manus Island and Nauru in the United States has progressed slowly, with more than 445 transferred by the end of last year.

Labor had promised to accept New Zealand's offer of resettling 150 refugees from Australia's offshore detention centres on Manus Island and Nauru, and also said it would look for a third country to accept more refugees.

The Coalition said it would cap Australia's refugee intake and has long refused New Zealand's offer.

Local hospital 'not able to cope'

Mr Boochani described the situation on Manus as "out of control", with many refugees locking themselves in their accommodation and refusing to eat.

"I have never seen Manus Island like this. I have never seen people like this," he said.

Both he and Mr Rintoul said the island's Lorengau Hospital was struggling with the influx of cases.

"The local hospital is simply not able to cope — some people who have self-harmed have been turned away from the hospital this morning," Mr Rintoul said.

Manus Provincial Health Authority could not be reached for comment.

The island's police chief, David Yapu, said three cases of attempted suicide and self-harm have been reported to police since the election, though he stressed that such incidents were not always reported.

Mr Yapu described the situation on Manus as "very critical" and called on authorities to address the "serious mental illness" among refugees on the island.

"I think it's something that both the PNG Government and the Australian Governments have to look at … because the more they [the refugees] live [here] they develop this stress and depression."

The Pacific International Hospital in Port Moresby is providing medical treatment to a number of refugees from Manus Island. ( ABC News: Natalie Whiting )

Medivac legislation faces repeal

Katie Robertson, legal director at the Human Rights Law Centre, said dealing with the "unprecedented medical crisis" was solely Australia's responsibility.

"What we are seeing is the result of six long years of an extremely punitive and cruel policy in which the Australian Government has deliberately and consistently denied refugees essential and critical medical care," she said.

"The Australian Government has, and has always had, the power — and indeed the legal obligation — to transfer refugees in its care to Australia for critical medical treatment."

A spokesperson for the Department of Home Affairs said in a statement that the Australian Government is "committed to supporting the Governments of PNG and Nauru by providing specialist and wide‑ranging health, welfare and support services".

It is unclear whether any of the refugees who have self-harmed in recent days will be transferred to Australia for medical treatment under the Medivac bill.

More than 40 refugees have been transferred off Manus and Nauru since the Medivac bill was passed in February, according to the Medical Evacuation Response Group (MERG).

MERG, a coalition of refugee support organisations, said it has received an average of 11.5 applications for assistance from refugees per day since then.

Treasurer Josh Frydenberg told reporters last week that the Government was committed to reversing the Medivac legislation, which Prime Minister Scott Morrison has previously said would "weaken our borders".