Saudi authorities are reviewing death penalties against three men convicted of crimes when they were minors, a statement said Thursday, as the kingdom seeks to improve its human rights record.

Ali al-Nimr, Dawood al-Marhoon and Abdullah al-Zaher, activists from the minority Shiite community, were arrested as minors in 2012 on terrorism-related charges after they took part in anti-government protests during the Arab Spring uprisings.

Citing a royal decree, the Saudi Human Rights Commission (HRC) in April said the kingdom was ending the death penalty for those convicted of crimes committed while they were under 18.

The public prosecutor ordered a review of the three cases this week, the HRC said in a statement.

"These referrals mark important progress in faithfully implementing an important reform in the legal system, and in advancing human rights in Saudi Arabia," HRC president Awwad Alawwad said in the statement.

"They demonstrate the critical importance of these reforms not just in changes to the legal code, but in actions." 

Campaigners said the families of the three detainees were not officially notified about the review and found out through the media. 

"The announcement to review the death sentences against these three young men is a significant and long overdue step towards justice," said Philip Luther, Middle East and North Africa research and advocacy director at Amnesty International.

"We call on the Saudi Arabian authorities to ensure that any retrial that follows is conducted in a fair, transparent and open manner... The authorities must also ensure that the 'confessions' extracted from them through torture are not used in proceedings." 

The kingdom has one of the world's highest rate of executions.

Individuals convicted as minors would receive a prison sentence of no more than 10 years in a juvenile detention facility, according to the HRC. 

Campaign group Reprieve also welcomed Thursday's announcement. 

"If the Saudi authorities are true to their word, and the death sentences of all people convicted of childhood crimes are to be reviewed, then this is a hugely positive development," said Reprieve's director Maya Foa, calling for the sentences to be commuted.

"Ali, Dawood and Abdullah were imprisoned as boys, and have spent almost a decade of their youth in fear of execution."

Reprieve said there were currently four people convicted of childhood crimes at risk of execution in Saudi Arabia, and prosecutors were seeking death sentences against another nine juveniles.

Crown Prince Mohammed bin Salman is aiming to blunt international criticism over the kingdom's rights record and its opaque judicial system, especially since the October 2018 murder of journalist Jamal Khashoggi.

In April, the HRC also announced Saudi Arabia was abolishing court-ordered floggings, in a move welcomed by campaigners.