An Iranian blogger and photojournalist faces "imminent death" for "blasphemous" Facebook posts in Tehran, human rights organisations warn.

Thirty-year old Soheil Arabi was convinced of insulting the Prophet Mohammed in September and last month the conviction was upheld by Iran's Supreme Court. It has now been revealed that officials have begun making preparations for his execution.

Arabi and his wife were arrested in November last year. She was later released, while he was transferred to Tehran's notorious Elvin prison where he was kept in solitary confinement, subjected to repeated abusive interrogations and denied access to his lawyer.

The court rejected his defence that he was in "poor psychological condition" when the crime was committed and that he had not written the posts himself, but simply shared the views of others on the social networking site.

According to Arabi's lawyer, the Supreme Court unlawfully added the charge of "sowing corruption of earth", to Arabi's case. In addition to carrying a death sentence, the charge also precludes the possibility of amnesty.

Human Right Watch says the ambiguous charge is often used by Iranian authorities to "prosecute, convict, and sentence political dissidents and others exercising their basic rights to freedom of speech, assembly, association, and religion."

Eric Goldstein from HRW said "it is simply shocking that anyone should face the gallows simply because of internet postings that are deemed to be crude, offensive, or insulting".

The group is calling on Iran to revise its penal code to stop the criminalisation of peaceful free expression, "especially when they punish its exercise with death".

Iran has one of the worst records of jailing journalists in the world. According to Reporters without Borders​, 65 journalists and bloggers are currently being held in Iranian prisons.