One of the world’s premiere organizations for spreading the message of the Bible in restricted nations says the underground Christian church in Iran is experiencing “explosive” growth.

“Forty years ago an estimated 200 Muslim Background Believers were living in Iran,” says a new report from Open Doors USA. “Today the estimation is 370,000 MBBs.”

Open Doors said the growth is happening in all regions of Iran but mostly in the larger cities.

Christians in the Islamic mullah-run nation constantly are targets for persecution. WND has reported recently the conflict between Iran and the Western world over  Christian pastor Youcef Nadarkhani, who was sentenced to death for leaving Islam for Christianity. Gene Kapp of the American Center for Law and Justice said what probably has been keeping the pastor alive is the international outcry against the sentence.

In Iran, house churches regularly are raided and congregants jailed, according to Open Doors

But the group reports that the surge of Christianity is looking like a revival.

One Open Doors worker in Iran, whose identity was concealed for safety, said, “Iranians are very outgoing and want to speak about their faith. That is why discipleship training (with elements of outreach and communications) for Iranian believers is successful. If you tell them that a Christian should share, the Iranian Christian shares.”

Besides new believers, Iran also has a traditional Armenian and Assyrian church with about 80,000 members. Those congregations are free to have meetings in their own language, but they are not allowed to evangelize Farsi-speaking Muslims.

“Open Doors workers think that the growth of Christianity has everything to do with Iranians getting to know the real face of Islam, the official religion of Iran, and the mistrust of the people toward the government and leaders following the fraudulent 2009 presidential election of Mahmoud Ahmadinejad,” the organization’s report said.

Many Iranians are seeing the biblical messages on satellite television, and Open Doors said Iran sees that as a threat.

“In 2010, Iran’s supreme religious leader Mahmoud Ali Khamenei blamed ‘the enemies of Islam for establishing and encouraging the expansion of Christianity in Iran.’ The minister of intelligence, Heydar Moslehi, reportedly warned of the threat of house churches and other Christian interests during October and November 2011,” Open Doors said.

“For that reason the house churches have to be more careful,” said another unidentified worker. “In the past every house church had around 15 members. Now this number of persons is five or six because of security reasons. Most of them are organized in networks and not connected to churches outside Iran.”

Iran, which is ranked No. 5 on the Open Doors 2012 World Watch List of the top 50 worst persecutors of Christians, recently prohibited churches from holding services in Farsi on Fridays.

“They thought this would lead to less people attending services, but that didn’t happen,” an Open Doors worker said.

Another restriction by the Iranian government is a ban on the sale of Bibles and New Testaments.

A recent report in Joseph Farah’s G2 Bulletin, the premium online newsletter published by the founder of WND, said persecution of Christians is on the rise throughout the Middle East as radical Muslims take over power from moderate dictators through the Arab Spring movement.

In Egypt, there are concerns about a pogrom.

Another recent report detailed a raid and arrest of members of a congregation in Shiraz by Iranian authorities.

At last report, they were being held in an undisclosed location.

Jihad Watch publisher Robert Spencer said that the Iranians don’t realize they are encouraging the growth of Christianity through persecution.

“They don’t know that Christianity grows amid persecution,” Spencer said. “Islam has expanded through violence and intimidation, so it isn’t at all surprising that they’d resort to it again.”

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