At least 90 people on death row in Iran are under the age of 18, says a group of UN experts who are calling for authorities in the Middle Eastern nation to immediately put an end to the execution of those aged who were under 18 at the time of sentencing.

Three UN experts - Asma Jahangir, special rapporteur on the situation of human rights in the Islamic Republic of Iran; Agnes Callamard, special rapporteur on extrajudicial, summary or arbitrary executions; and, Benyam Dawit Mezmur, chairperson of the Committee on the Rights of the Child - made the call late last week amid news that a man who was aged 15 at the time of his sentencing will be executed next week.

Peyman Barandah was just 15-years-old when he was sentenced to death in 2012 for the fatal stabbing of a teenager. His execution will now be carried out on 10th May.

The announcement of the date comes after another execution - that of Mehdi Bohlouli who was 17-years-old when sentenced to death in 2001, also for the fatal stabbing of a man - was halted just a few hours before it was due to take place on 19th April. It is not clear when Mr Bohloudi's execution will now be carried out.

“We are dismayed by the unprecedented rise in the number of cases of execution of juvenile offenders in Iran,” the experts said in a statement. “The psychological suffering inflicted on adolescents kept languishing for years in prison under a death sentence is appalling, and amounts to torture and ill treatment.”

Calling for both of the executions to be "halted immediately" and the death sentences quashed, the three experts also called on Iran to "commute without delay all such sentences imposed on children".

The experts said the two cases take to six the number of juvenile offenders scheduled for execution in Iran since January, including the cases of two whose sentences have been carried out. They added that while the Iranian Government had assured the UN Committee on the Rights of the Child in 2016 that a 2013 amendment to the country's penal code opening the possibility for juveniles sentenced to death to be allowed retrials would be systematically applies to all juveniles then on death row, "these promises have not been fulfilled".

They noted that by ratifying both the International Covenant on Civil and Political Rights and the Convention on the Rights of the Child, Iran had committed itself to protecting and respecting children’s right to life as well as to outlaw the death penalty for all those under the age of 18.

“Any assumption that a girl over nine years old or a boy older than 15 can be considered mature enough to be sentenced to death, infringes on the very basic principles of juvenile justice and violates both treaties,” they said. "Furthermore, any death sentence undertaken in contravention of a government’s international obligations, notably its duty to establish a juvenile justice system in line with international human rights standards, is unlawful and tantamount to an arbitrary execution."