By Pam O'Toole
BBC News
Behnam Zare was the second Iranian in a week to be put to death for a crime he committed when he was under 18 and the sixth such execution in 2008.
Human rights groups say neither Zare's family nor his lawyer were notified prior to the execution.
Iran is the only country known to have executed people this year for crimes committed while they were minors.
Behnam Zare was convicted of murder after killing another young man in a street fight three years ago.
One Iranian newspaper said Zare, who was 15 at the time, had told the court it had been an accident and he had asked the victim's family for forgiveness.
But on Tuesday he was hanged in a prison in the southern city of Shiraz.
Abhorrent practice
International human rights organisations have condemned Zare's execution. Human Rights Watch said Iran led the world in executing juvenile offenders.
Everywhere else, it said, countries were moving to end what it called this abhorrent practice, but in Iran the number of death sentences seemed to be increasing.
Amnesty International said the situation of juvenile offenders facing execution in Iran had reached a crisis level with at least 132 of them known to be on death row.
The execution of Behnam Zare follows that of another juvenile offender, Reza Hejazi, just a week ago.
In both cases, their lawyers were reportedly not given 48 hours notice of the impending executions, as required by Iranian law.
In the case of Behnam Zare, human rights groups say, his family was also given no advance notification.
Iran was second only to China in the number of overall executions it carried out in 2007 for crimes including murder, rape, drug-trafficking and armed robbery.
Amnesty says so far this year at least 227 people have been executed in Iran.
