An Iranian pastor has been charged with waging war against God or "Moharebeh" – a crime punishable by death.

Pastor Matthias Haghnejad was arrested at his home by Iranian security forces on the morning of July 5 along with two friends, Mohammad Roghangir and Suroush Saraie.

Several Bibles were confiscated from the pastor's house during the arrest, along with pamphlets and a personal computer.

According to Christian Solidarity Worldwide, sources have now revealed that pastor Matthias was interrogated for two hours on August 3 by Judge Mohammed Yari of the Sixth Branch of the Revolutionary Tribunal of Karaj. Following this interrogation, he was charged with "Moharebeh".

He has already served three jail sentences, but CSW now fear that his latest charge "may herald a worrying escalation in Iran's campaign against converts to Christianity."

Until now, Christian converts have usually been accused of national security crimes such as "action against state" or "action against the order".

The 2013 Islamic Penal Code forbids the death sentence for "Moharebeh" unless a weapon is used, yet eight men, including a poet and cultural rights activist, have been executed for the crime so far this year.

Those accused of "Moharebeh" often say they were not given legal assistance, and some have insisted they were forced to give a false confession under circumstances of torture.

"We urge the Government of Iran to end its harassment of Pastor Matthias," chief executive of CSW Mervyn Thomas said in a statement.

"Levelling a charge of warring against God against a man whose role and calling precludes violence and emphasises service and obedience to God is unjustifiable, implausible and tantamount to an indictment of Christianity itself.

"These charges constitute a worrying escalation of Iran's campaign against Christians, adding a sinister new component to the regime's appalling litany of religious freedom violations. The fact that Iran continues to commit severe human rights violations, including executions without due process and on vague charges, while simultaneously seeking improved relations with other nations, is a matter of utmost concern."

Thomas concluded by calling on international government to "insist on discernible and consistent improvements in human rights, and on the upholding of rights stipulated in international covenants to which Iran is party, as benchmarks for improving bilateral and multilateral relations."

Christian converts are forbidden from praying in public churches in Iran and American pastor Saeed Abedini, who is serving an eight-year prison sentence for "threatening the security of the state," remains in jail for his involvement in developing home church communities.