"The ongoing raiding of homes and arrests of Christians in predominantly Shi’ite Iran, which began deplorably during the Christmas season, need to stop immediately," said the Religious Liberty Commission of the World Evangelical Alliance in a statement Wednesday.

Since Christmas, about 70 Christians have been arrested and several media reports indicate that Iranian authorities are targeting converts from Islam or those seeking to convert Muslims.

According to the official Islamic Republic News Agency, Tehran Governor Morteza Tamadon claimed that the Christian missionaries had stepped up their activity in Iran and, "like the Taliban," have "inserted themselves into Islam like a parasite".

He said more arrests will be made.

WEA-RLC Executive Director Godfrey Yogarajah called the recent crackdown "condemnable" and "incongruous" given that Shi'ites face persecution in Sunni-majority countries like Pakistan.

He observed, "The growing authoritarianism in Iran only shows that the regime’s popularity is falling drastically which is making the government highly insecure and unnerved."

Over the last few weeks, Iranian security agents have been raiding the homes of Christians, searching for Bibles, religious books and pictures, confiscating computers and personal documents, and making arrests.

The crackdown comes months after Iran's intelligence minister said that his agents had discovered hundreds of underground church groups, including 200 in the Muslim holy city of Mashad, as reported by NPR.

Along with the arrests, the WEA commission also drew attention to the detainment of two Christian pastors, Behrouz Sadegh-Khanjani, who is facing a possible indictment for apostasy, and Youcef Nadarkhani, who was charged with apostasy and sentenced to death.

Among 67 million people, 98 percent are Muslim and largely Shi'a.

The Iranian government has a poor religious freedom record, regularly cracking down on its religious minorities, including Christians, Sufi Muslims and Baha’is. The latest report by the US State Department revealed that respect for religious freedom in Iran continued to deteriorate and that government rhetoric and actions "created a threatening atmosphere for nearly all non-Shi'a religious groups".

Reports of government imprisonment, harassment, intimidation, and discrimination based on religious beliefs have continued, the report further stated.

Persecution watchdog Open Doors recently listed Iran as the second worst persecutor of Christians in the world as Christians continued to be arrested "in waves".

Church services are monitored by secret police and believers are often questioned and beaten, according to Open Doors. Despite the persecution and hard-line Islamist regime, the watchdog reported that the number of Christians continues to grow and that currently there are at least 450,000.