An Iranian 21-year-old has been sentenced to death after 'insulting the prophet' of Islam on an instant messaging app.

Sina Dehghan was 19 when he was arrested by the Iranian revolutionary guard at a military barracks in Tehran in October 2015 for insulting the national religion on the messaging app LINE.

Human rights activists claim that Dehghan was fooled into singing his own confession under the belief that he would be released without punishment if he did so.

But after signing the confession, prosecutors dropped the agreement and kept Dehghan incarcerated at Arak Prison.

Sina Dehghan was 19 when he was arrested by the Iranian revolutionary guard at a military barracks in Tehran in October 2015 for insulting the national religion on the messaging app LINE

His death penalty was confirmed in January when it was upheld in the country's Supreme Court, according to the Center for Human Rights in Iran (CHRI).

'During his interrogation, Sina was told that if he signed a confession and repented, he would be pardoned and let go,' a source told CHRI. 'Unfortunately, he made a childish decision and accepted the charges. Then they sentenced him to death.'

The content of Dehghan's messages is unknown.

The source said that authorities got Dehghan to confess on camera as well, and that authorities told his family that if they kept quiet about the charges, Dehghan would be more likely to be freed.

'Unfortunately, the family believed those words and stopped sharing information about his case and discouraged others from sharing it as well,' the source said.

Branch 1 of the Criminal Court in Arak had asked that Dehghan be sentenced to death for 'insulting the prophet' as well as 16 months in prison for 'insulting the supreme leader'.

A request for a judicial review of the death sentence that was issued in January is being processed, Dehghan's lawyer said

A request for a judicial review of the death sentence that was issued in January is being processed, Dehghan's lawyer told CHRI.

'According to Sina's lawyer, steps have been taken for a judicial review, and with the good news we're hearing from him, God willing this case will come to end positively as soon as possible,' Dehghan's mother said in a video obtained by CHRI.

Dehghan's co-defendants, Sahar Eliasi and Mohammad Nouri were also convicted of posting anti-Islamic material on social media.

Nouri was issued a death sentence, but it is unknown if the Supreme Court has issued a final ruling.

Eliasi had a seven-year prison sentence reduced to three after going to appeals court.

Dehghan, who was a conscript posted as a guard in military barracks, had just four days left in his military service when he was arrested in 2015.

'They took him to his home and searched it while he repeatedly expressed regret and repentance,' a source told CHRI.

According to Iran's Islamic Penal Code, insulting the prophet is punishable by death. Article 263 of the document, however, states that if the accused tells the court that the insults were a result of anger or a mistake, the sentence can be reduced to 74 lashings.