Rights watchdog Amnesty International says it is "outraged" at the execution in Iran of a young man convicted of a murder he committed when he was 15.

The group said in a January 30 statement that 22-year-old Ali Kazemi was hanged earlier the same day in a prison in Bushehr province.

"His execution was scheduled and carried out without any notice given to Ali Kazemi’s lawyer as required by Iranian law," Amnesty said.

“By carrying out this unlawful execution, Iran is effectively declaring that it wishes to maintain the country’s shameful status as one of the world’s leading executers of those who were children at the time of their crime,” said Magdalena Mughrabi, Amnesty International’s Middle East and North Africa Deputy Director.

“This is nothing short of an all-out assault on children’s rights, as enshrined in international law, which absolutely bans the use of the death penalty against someone who was under 18 years of age at the time of the crime.”

Kazemi was convicted in connection with the fatal stabbing of a man during a fight in March 2011, when he was only 15.

“It is long overdue for the head of Iran’s judiciary to intervene and establish an official moratorium on executions of juvenile offenders.

Iranian parliamentarians must amend the Penal Code to ban the use of the death penalty against anyone who was under 18 at the time of the offence,” Mughrabi said.

Amnesty said it has found that prison officials and prosecutors in Bushehr "tormented Ali Kazemi’s family by making contradictory statements as to whether and when the execution would be carried out." There was no immediate comment from Iranian officials.