A Sri Lankan refugee who died on Manus Island on Monday was due to face court on sexual assault charge the day his body was found.

The 32-year-old man was charged with sexually assaulting a woman in a hotel in Lorengau, the town on Manus Island, in January.

He denied the charge, saying the pair were in a relationship and had consensual sex.

But the case went ahead and the man was to face a committal hearing on Manus Island on October 2, when his body was found in the laundry at the Lorengau Hospital.

Manus Province police commander David Yapu said the man had been taken to hospital for treatment on September 29, after trying to harm himself.

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"His body was found [on October 2] by the hospital staff and reported to Police and Papua New Guinea Immigration & Citizenship Authority Services (PNGICSA)," he said.

"The forensic team from Port Moresby with local Police and PNGICSA attended to the scene and retrieved the body.

"The deceased's body was placed in a temporary cooler at the hospital and will be taken to Port Moresby for autopsy to determine the cause of death."

Friends said the man had been increasingly distressed since leaving the Manus Island detention centre to live in a transit centre in Lorengau.

Fellow Tamil refugee Shamindan Kanapadhi said his friend had asked for help but had not received treatment for mental illness.

"There is no facility to help those who are mentally ill," he said.

"The only thing is they could get support from a private counsellor, so if they had given proper treatment for this fellow why should he go and [kill] himself."