Amnesty International has called on Iran to immediately halt plans to execute three young men who are on death row for crimes committed when they were under the age of 18.

The London-based rights group said on February 22 it had learned that Mohammad Kalhori, Barzan Nasrollahzadeh, and Shayan Saeedpour -- all convicted for separate crimes that took place while they were minors -- are at risk of "imminent" execution.

"The Iranian authorities must act quickly to save these young men's lives. Failing to stop their execution would be another abhorrent assault on children's rights by Iran," Saleh Higazi, deputy Middle East and North Africa director at Amnesty International, said in statement.

"International human rights law strictly prohibits the use of the death penalty against people who were under the age of 18 when the crime was committed," Higazi said.

Iran is among a handful of countries that executes juvenile offenders.

Amnesty International said it was aware of more than 90 cases of people in Iran currently on death row for crimes that took place when they were under 18. The rights organization said the real number is likely to be far higher.

Kalhori was 15 years old when he was arrested in December 2014 over the fatal stabbing of one of his schoolteachers, the rights group said.

According to Amnesty International, Nasrollahzadeh was arrested by the Ministry of Intelligence at the age of 17. He has said that he was tortured while in detention. He was later sentenced to death on charges of "enmity against God."

The rights group said Saeedpour was arrested when he was 17 for a murder committed during a fight in 2015. Saeedpour was sentenced to death for first-degree murder in 2018.

Amnesty said it had noted an "alarming pattern" by the Iranian authorities, who schedule executions of juvenile offenders at short notice in order to minimize the chances of public or private interventions for a reprieve.

It called on Iran's parliament to urgently amend Article 91 of the 2013 Islamic Penal Code to abolish the death penalty for crimes committed by people under 18 in line with Iran's international obligations.

Iran is one of the world's leading executioners. Amnesty said in April that 507 people were executed by the Iranian authorities in 2018, including at least five juvenile offenders.