Iranian security forces in Shiraz dismantled a network of four underground “house churches” on Sunday night, and arrested their leaders.The Persian-language service Fars News, which is close to the Iranian Revolutionary Guards Corps, on Monday described the churches as a “network of criminals” that exploited vulnerable people.“Most people attracted to these networks come from weak and vulnerable segments of society, who have psychological, emotional and economic problems,” the report said, echoing a recent warning by a prominent Qom cleric.In June, Qom’s Friday prayer Imam Hojatoleslam Seyed Mohammed Saeedi told the Organization of Islamic Propaganda that Iran’s enemies targeted vulnerable families in order to establish underground “house churches,” according to Iranian Christian news agency Mohabat News, which works to report violations of Christians’ rights in the country.Monday’s Fars News report blamed the growth in underground Christian houses of worship on the spread of “Zionist propaganda.”“It is interesting to note that this illegal network is affiliated to Zionist propaganda deployed from outside the country,” the report said, although Fars did not specify how the Christian churches were linked to any Jewish or Israeli groups, or explain why it believed Jewish organizations would promote Christianity in Iran.While Fars News did not report the number of arrests, UK-based group Christian Solidarity Worldwide said on Sunday that seven Christians had been arrested in the Shiraz raid, and were being held in the Shiraz Intelligence Office’s notorious No. 100 detention center.Sunday’s arrests are the latest in a wave of detentions in Shiraz. In the past few weeks, Iranian Intelligence Ministry agents in the city have arrested around 30 Christian converts and transferred them to the No. 100 detention center, according to Belgian-based Persian-language news site Gooya.Iran’s constitution grants protection to non-Muslims born into other religions, including Jews and Christians.However, under Iranian law, evangelizing and converting Muslims to other religions is illegal. Apostasy – converting to another religion from Islam – is technically punishable by death, unless the convert renounces his religion and returns to Islam.Over the past year, religious minorities have reported increased crackdowns and persecution by regime officials, causing concern among human rights activists. Last month, the UN’s special rapporteur on the situation of human rights in Iran, Ahmed Shaheed, estimated that more than 300 Iranian Christians had been arrested and detained since June 2010.Churches were also reporting “undue pressure to report membership [to the Intelligence Ministry] in what appears to be an effort to pressure and sometimes even detain converts,” Shaheed said.On Sunday, a Christian artist and convert from Islam, Vahid Zarday, was released from Vakil-Abad Prison in Mashhad after 136 days of detention.Zarday was arrested in May, also for attending a religious service in a “house church,” but the Iranian authorities would not give details of Zarday’s release, according to Mohabat News.