The family of 24-year-old asylum seeker Hamid Kehazaei, who died in a Brisbane hospital after a severe leg infection, has demanded justice.

Ruth Hudson, the solicitor acting on behalf of Mr Kehazaei's family in Iran, said his shattered mother and brother were demanding to know why his life had been lost to a treatable infection.

Hamid Kehazaei.

Ms Hudson said that by the time Mr Kehazaei, a Manus Island detainee, was transferred from a Port Moresby hospital to the Mater Hospital in Brisbane, he was already "gravely ill".

Immigration Minister Scott Morrison confirmed the asylum seeker's death on Friday night in Brisbane's Mater Hospital, where he had been on life support for a week.