The Sudanese refugee who died after falling ill on Manus Island had been turned away from the detention centre's medical provider amid accusations he was pretending to be sick, a fellow detainee has alleged.

Key points: Fellow detainee Abdul Aziz Adam says Faysal Ishak Ahmed had sought medical treatment every few days for several months

Fellow detainee Abdul Aziz Adam says Faysal Ishak Ahmed had sought medical treatment every few days for several months Mr Ahmed told by medical clinic to "please stop coming here" for "pretending to be sick", Mr Adam says

Mr Ahmed told by medical clinic to "please stop coming here" for "pretending to be sick", Mr Adam says Doctors for Refugees spokesperson says offshore detention a "recipe for disaster"

Faysal Ishak Ahmed, 27, collapsed at the centre's Oscar compound on Thursday. He was evacuated to Brisbane for urgent treatment on Friday, but died in hospital.

The Immigration Department said Mr Ahmed had suffered a seizure and there were no suspicious circumstances.

But fellow detainee Abdul Aziz Adam, 24, said Mr Ahmed had sought medical treatment from the clinic, run by International Health and Medical Services (IHMS), every few days for several months for various ailments including stomach upsets, high blood pressure, fevers and heart problems.

"[Mr Ahmed] said 'I don't get to see the doctor, I always see the nurse and then the nurse tells me 'you don't have anything', but I feel I have a problem'," he said.

Mr Adam said he and about 60 asylum seekers signed a letter addressed to IHMS demanding better medical treatment for Mr Ahmed after he returned from the clinic earlier this month looking particularly crestfallen.

"He said 'I went to the IHMS and then the IHMS told me that, hey you don't have anything, you are not sick and you're pretending to be sick, and from now on, we don't want you to come down here, so please stop coming here'," he said.

"And we were very, very devastated at that moment when he told us that story."

'The system is designed to kill us one by one'

Mr Adam said Mr Ahmed had been in detention since late 2013, having fled Sudan — where his parents and brother still live — and tried to come to Australia by boat.

Abdul Aziz Adam (pictured) is a detainee on Manus Island. ( Facebook: Abdul Aziz Adam )

He said they were both granted refugee status about two years ago.

Mr Ahmed enjoyed painting, reading and writing, Mr Adam said, and was always smiling, even if he was in pain.

"I can't hold my tears because how does this happen?" he said.

"Two days ago I spoke with him on the phone, now he end up dead.

"This system is designed to kill us one by one."

The Immigration Department said it had referred the case to the Queensland Coroner but declined to comment further.

IHMS did not respond to the ABC's requests for comment.

'It's clearly a recipe for disaster'

Dr Barri Phatarfod from Doctors for Refugees said Mr Ahmed was the latest needless death arising from the poor standard of healthcare on Manus Island.

A coronial inquest has been scrutinising medical evacuation procedures off Manus Island. ( Refugee Action Coalition )

She said Mr Ahmed's pleas for help went unanswered.

"Somebody has ignored it," she said.

"Now whether that's IHMS, whether that's the department, presumably that will come out in yet another coronial inquest.

"There'll be records that these complaints and these symptoms and these presentations have been made over several months."

She said Australia's offshore detention system was a failure.

"It's clearly a recipe for disaster and we're not talking about old, infirm people here — not that that would make it any more palatable," she said.

"Hamid Khazaei was 24 when he died. This young man was 27."

The Queensland Coroner is currently investigating Mr Khazaei's death in 2014 from a leg infection.

The inquest has been scrutinising medical evacuation procedures off Manus Island, and will resume in February.