Even convicts on death row could escape capital punishment, according to Tehran's prison service chief on Monday.

Speaking to the student news agency ISNA, Sayyid Morteza Bakhtiari said "prisoners... can benefit from certain measures if they learn the Koran by heart, even if they are condemned to death."

The prisons chief spoke of "facilities for their release", without specifying if that would also apply to convicts facing the death sentence.

Three hundred clerics and 200 theology students are currently taking classes in the Islamic republic's jails, he added.

Gulf Arab states have also offered to shorten the sentences of convicts who learn the Quran by heart.

There are conditions, however. Under Islamic law, it is up to the family of a murder victim to pardon a convicted killer.