A Iranian asylum seeker in detention on Nauru has staged a protest by climbing to the top of a crane to demand the release of all children from detention.

Reza Khestinzhad has climbed a crane on Nauru to protest at the detention of children carrying a banner reading: “World: Kids in Nauru Need Help” Photograph: none

Reza Khestinzhad has been held in detention on Nauru, with his sister, for 21 months. He scaled the crane early on Friday and refused to come down for nine hours.

When he came down voluntarily on Friday night, he was taken for medical checks.

He spoke to Guardian Australia by phone from the crane, saying that children on Nauru were desperate “because they have no future”.

“My position here is very bad, but I have to give my message. The children on Nauru need help, they have been here too long. We are all suffer[ing] here, we are all depress[ed], we are all on medication because our health is bad.

“But it is the worst for the children. They should be free.”

He is carrying a massive banner he made that reads World: Kids in Nauru Need Help.

Currently, there are 95 children in detention in Nauru.

Instances of child sexual and physical abuse, psychological trauma, and disproportionate rates of depression, have been consistently reported from the island.

Senate estimates heard last month that in the two years to the end of September, there were 10 instances of sexual abuse against children, and 82 incidents of physical assault.

No one has ever been charged for an assault against an asylum seeker on Nauru.

The crane Khestinzhad climbed is in the detention centre as part of the construction of a new accommodation block. Many of those in detention still live in tents.