On the day an Iranian asylum seeker died in a Brisbane hospital after he set himself alight on Nauru, nearly 200 people rallied in King George Square to call for an end to offshore detention.

The man, believed to be called Omid, died of his injuries in the Royal Brisbane and Women's Hospital on Friday afternoon after he was flown into Australia for emergency medical treatment.

Paul Mansfield wears a cage symbolising the imprisonment of asylum seekers. Credit:Cameron Atfield

Omid's death hung heavy on the crowd that gathered in Brisbane's CBD Friday evening.

"That young man is lying up the road, in that hospital in Herston, and that young man needs to be a reminder to this government that we will not take their treatment of human beings like this anymore," Karen Anderson, the Greens candidate for Griffith, told the rally.