A US-based human rights organisation has called on Iran to end the execution of juvenile offenders.
Iran is one of only five countries to continue executing juveniles
Human Rights Watch (HRW) said Iran was in breach of international agreements it had signed up to.
The call follows last week's public hanging of two youths convicted of still unclear sexual offences.
Iran insists the youths were convicted of raping a younger boy. However gay rights organisations say the youths were executed for being homosexual.
The case has had considerable global resonance.
Leading European and US gay organisations and publications have already launched letter-writing protest campaigns, and plan to hold demonstrations outside Iranian embassies over the coming weeks.
In a statement issued on Thursday, HRW said Iran was one of only five countries to continue executing juveniles and called for an end to what it called an inhumane punishment.
The Iranian judiciary has reacted angrily to the international outrage surrounding the public hanging of Mahmoud Asgari and Ayaz Marhoni, whom rights activists claim were aged 16 and 18.
Officials said they had been sentenced to whipping and hanging for rape, drinking alcohol and disturbing public order, and deserved the punishment they got.
Rare, close-up pictures of the execution were rapidly published on the internet. In them, officials can be seen placing nooses around the necks of the two obviously distressed, young men.
Public executions are not unusual in Iran but the execution of juveniles often attracts international opprobrium.
The case has been adopted as a cause celebre by gay rights groups.
They say the majority of media reports suggest the official charges were fabricated to reduce any public sympathy for the youths and that the real reason was the youths' sexual orientation.
Homosexuality is illegal in almost all Muslim countries, and punishable by death in many of them.
But gay and human rights groups say Iran's record is particularly shocking, having executed possibly thousands of gay men since the Islamic revolution.