Another young refugee on Nauru is critically ill after refusing to eat and drink, and rejecting medical care for weeks, while a 12-year-old girl has been taken to Nauru hospital after reportedly attempting to set herself on fire.

The situation on Nauru has grown “dangerously chaotic” a government source told Guardian Australia.

A 17-year-old girl is being treated inside the regional processing centre after refusing all food, fluid and medical treatment. The girl, S (Guardian Australia has chosen not to publish her name), is one of several children doctors say are critically ill on the island.

Three separate doctors on the island have written overseas medical referrals for S stating she should be urgently moved to a hospital off the island. They have diagnosed S with major depressive disorder and ‘resignation syndrome’, and recommended admission to an inpatient unit.

S has been inside the supported accommodation area of the regional processing centre for three weeks, and has been refusing food and water for much of that time.

Medical sources report her condition has deteriorated badly in the last 24 hours, and she is now one of the most critical cases on the island. There are several children who are severely or critically unwell on the island at present.

A source familiar with the girl and her condition, said she had previously been one of the brightest and most articulate of the refugee children.

“Before she got sick, she was the best-performing student. She had a dream to be a doctor in Australia and to help others. Now, she is on food-and-fluid refusal and begging to die as death is better than Nauru.”

Also on Wednesday, a 12-year-old refugee girl attempted to set herself on fire. Family and friends intervened, but she has reportedly sustained some injuries. She is being treated at the Nauru hospital.

The girl has made repeated attempts to kill herself in recent weeks, and the incident was witnessed by several other children.

The girl was seen by a psychiatrist on the island last week who recommended she be moved to Australia.

Several adults have set themselves on fire on Nauru, one fatally, and a number of children have attempted to kill themselves by that method.

M, a 12-year-old refugee boy who had previously been refusing to eat for 20 days, was flown critically unwell to Brisbane on Tuesday afternoon – four days after doctors had recommended he be urgently moved to hospital – in an air ambulance.

The Australian Border Force had initially refused to take him with his family, but the family resisted being separated, possibly permanently. After doctors repeatedly demanded he be moved to care, and refused to forcibly feed him, arguing it was unethical, he was transferred.

The boy weighed 36kg and was unable to stand by the time the ABF acquiesced to his transfer with his entire family.

M is being treated at Brisbane’s Lady Cilento hospital. He remains seriously unwell, and is being fed via nasogastric intubation.

His stepfather is with him in the hospital but Guardian Australia understands his mother and sister are being held not in the community, but in immigration detention in Brisbane.

They are being allowed to visit the boy.

On Nauru, sources say they are growing increasingly fearful of a growing “contagion” of children committing self-harm, attempting suicide or refusing all food and fluid.

Other children have been diagnosed with the rare but serious child psychiatric disorder pervasive refusal syndrome, also known as resignation syndrome, which has been documented at high rates among asylum seeker children, especially in Sweden.

Children suffering resignation syndrome effectively withdraw from life – refusing to eat, drink, toilet, leave their beds, speak, or even open their eyes. They are sometimes completely unresponsive to stimuli.

There are also growing concerns that the next month’s Pacific Islands Forum – envisaged as a showcase for Nauru in its 50th year of independence – will be entirely overshadowed by the situation of critically ill children who have been held on the island more than five years.

Self-harm and suicide attempts – including by self-immolation – are growing routinely common on the island, among both adults and the 117 children who remain on the island.

Guardian Australia has consistently approached the Department of Home Affairs – now being run, absent a permanent minister in the portfolio, by former immigration minister Scott Morrison – for comment on child cases on Nauru. The department has consistently said it “does not comment on individual cases”.

The department’s chief medical officer, Dr Parbodh Gogna has declined repeated interview requests.

He told Senate estimates this month the medical services on Nauru were better than those in regional and rural Australia.

“It’s very well staffed. There are significant assets there. There’s near-patient pathology. There’s expertise in specialists. It’s something that the Australian government should be proud of.”

• Readers seeking support and information about suicide prevention can contact Lifeline on 13 11 14 or Suicide Call Back Service 1300 659 467. Other international suicide helplines can be found at befrienders.org