A 12-year-old refugee boy on hunger strike on Nauru for more than a fortnight is at imminent risk of dying, medical staff on the island say, but efforts to move him to hospital care in Australia have foundered.

He is one of several critical child cases on the island – including a 14-year-old boy with muscle wastage so severe he may never walk normally again, and a two-year-old child whose parents are too unwell to care for him.

Staff on the island report a looming crisis in children’s health, ahead of the Pacific Islands Forum next month, and the attendant international attention that will bring.

“Everyone on the island knows how serious this is. We have been saying for months a child is going to die in these circumstances,” an on-island official with knowledge of the medical situation told the Guardian. “A child is going to die. Every day we get closer. It’s never been so critical.”

The 12-year-old boy has been held on Nauru with his mother, father and sister for nearly five years. The family, from Iran, have been recognised as refugees but were recently rejected for resettlement in the US. Almost all Iranian refugees have been rejected by America.

The boy has refused food and fluids for between eight and 15 days, medical sources on the island say. He is being sedated so he can be given fluids intravenously to keep him alive.

“The situation is critical. They know about this in Canberra but nothing is happening,” another source on the island said.

There are several critical children’s health cases on the island currently.

Two children are expected to leave the island on Friday. One is an eight-year-old autistic boy who requires high-level care not available on Nauru and who has not been able to attend school.

His parents are both seriously unwell, in particular his mother, who has been “catatonic”, according to reports, for more than a year. Medical reports, running back more than a year, consistently request he be removed from the island with his family.

A 14-year-old boy who has not left his bed for more than four months is also being taken from the island. The boy’s mental health has deteriorated so badly he no longer feeds, cleans, toilets or cares for himself.

Medical staff have reported he has muscle wastage so severe, he might never regain the strength to walk properly again.

The Guardian has seen medical reports for these children, but is not publishing their names or any identifying details. Both are expected to leave Nauru on Friday, and other unwell children are also slated to leave.

However, other children, including the child on hunger strike, are not moving.

There are currently about 130 children held on Nauru, and all but a handful have been recognised as refugees.

A two-year-old child was left in the care of staff on the island – who had to care for the boy around-the-clock on a roster – after the child’s mother attempted suicide at the front gate of the processing centre and was too unwell to care for him. The child is now in the care of another family member.

And an air ambulance arrived on the island several days ago to take a seriously ill 15-year-old refugee boy to Taiwan. But after protests from his family, and concerns over his fitness to fly, the plane left without a patient.

IHMS staff have made repeated demands the boy be moved from Nauru to a place where higher-level care is available. The ABF has maintained the boy and his family have refused treatment, citing the plane being turned away (at a cost of more than $100,000).

Since December, at least 14 legal challenges have been brought before the federal court seeking immediate orders that children be moved from Nauru to a place where higher-level care is available, almost invariably Australia.

Each challenge has been opposed by the government but each has been successful: every case has either been conceded by the government at the courthouse door, or resulted in an order from the bench that children be moved immediately.

In one case involving a teenage girl, heard last month, the court heard children on the island had been diagnosed with the severe “major depressive disorder and pervasive refusal syndrome” – a rare but serious child psychiatric disorder, also referred to as “resignation syndrome”, which has been documented at high rates among asylum seeker children, especially in Sweden. Children refuse to eat, drink, talk, walk, or toilet themselves, in some cases even open their eyes.

Privately, Australian and Nauruan government officials are deeply concerned about the upcoming Pacific Islands Forum, and the influx of media and political attention the Pacific leaders’ event will bring. There are concerns the welfare of asylum seekers and refugees on the island – most particularly the mental health of children – will be exposed by reporters from across the region allowed rare access to the usually off-limits island.

Media on the island have been limited for the forum – ostensibly for but also out of concern the welfare of refugees and asylum seekers will be investigated by journalists, or the forum will be overshadowed by large-scale protests on the small island.

The Guardian’s application to attend the Pacific Islands Forum was rejected. The ABC was also publicly told it would not be allowed on the island because of its “lack of respect”.

The Guardian has put questions regarding children’s healthcare on Nauru to the Australian government.