Iran has arrested about 70 Christians since Christmas in a crackdown that demonstrates the limits of religious tolerance by Islamic leaders who often boast that they provide room for other faiths.
The latest raids have targeted grass-roots Christian groups that Iran describes as "hard-liners" who pose a threat to the Islamic state. Authorities increasingly view them with suspicions that range from trying to convert Muslims to being possible footholds for foreign influence.
Christian activists contend that their Iranian brethren are being persecuted simply for worshipping outside officially sanctioned mainstream churches.
Caught in the middle is the small community of Iranian Christians who get together for prayer and Bible readings in private residences and out of sight of authorities. They are part of a wider "house church" movement that has taken root in other places with tight controls on Christian activities such as China and Indonesia.
Iran's constitution gives protected status to Christians, Jews and Zoroastrians, but many religious minorities sense growing pressures from the Islamic state as hard-edged forces such as the powerful Revolutionary Guard exert more influence.
Groups monitoring Christian affairs in the Islamic world say Iranian authorities see the unregulated Christian gatherings as both a potential breeding ground for political opposition and suspect they may try to convert Muslims in violation of Iran's strict apostasy laws -- which are common throughout the Muslim world and have at times fed extremist violence against Christians and others.
The crackdown by Iran resonates forcefully across the Middle East at a time when other Christian communities feel under siege following deadly attacks against churches in Egypt and Iraq -- bloodshed that was noted Monday by Pope Benedict XVI in an appeal for protection of religious minorities.
Tuesday, an off-duty Muslim policeman opened fire on a train in southern Egypt, killing a Christian and wounding five others less than two weeks after the New Year's Day bombing at a church in Alexandria that killed 21 Coptic Christians, according to the state news agency. There were few details on the incident, and it was unclear whether the shooting was sectarian related.
The suicide blast in Egypt's Mediterranean port of Alexandria on Jan. 1, which killed the Coptic Christian worshippers, followed threats by al-Qaida in Iraq over claims that Coptic leaders forced two women who converted to Islam to return to Christianity -- allegations that church leaders deny.
There are no accurate figures on the number of Christians in the "house church" movement or followers outside established denominations. But the manager of the Iranian Christian News Agency, Saman Kamvar, said authorities likely perceive some kind of challenge to the religious status quo and are "feeling insecure."
Kamvar attributes the stepped-up raids against Christians to comments last month by Iranian Supreme Leader Ayatollah Ali Khamenei denouncing the growth of private house churches.
"This, in my opinion," Kamvar said, "was a green light to the other authorities to crack down on them."