Iranian authorities have reportedly transferred imprisoned U.S. citizen Saeed Abedini to a dangerous prison, prompting concern from human rights groups and calls for U.S. leaders to secure the Christian pastor's safety.

"Pastor Saeed is now in one of the most dangerous wards of Rajai Shahr Prison – where violent prisoners are held, those who are imprisoned for murder and rape," Jordan Sekulow of the American Center for Law and Justice said Nov. 4.

"The transfer to this prison is a deeply disturbing development and can only be viewed as a move that puts Pastor Saeed's life directly at risk," he added. "This new and extremely dangerous development requires the full attention and focus of President Obama. He must speak out now – directly and forcefully – to save Pastor Saeed's life."

Abedini was imprisoned in September 2012 on charges of threatening national security, but human rights groups contend that his Christian faith is the real motive for his eight-year sentence.

He was raised Muslim in Iran and converted to Christianity in 2000. He married a U.S. citizen and became a U.S. citizen himself in 2010.

After his conversion, Abedini worked with house churches throughout Iran until 2009. Although the churches are technically legal, the government raised objections to his work. Since 2009, the pastor has worked only with non-religious orphanages in the country. He was arrested during a trip to visit these orphanages last fall.

Family members confirmed that the pastor was recently moved from Tehran's Evin Prison to Rajai Shahr Prison in Karaj.

In 2005, Dutch diplomat Loes Bijnen described the prison as a place of "severe punishment" where "nuisance" political prisoners are sent. He said these prisoners have to share cells with dangerous criminals who "don't hesitate to attack their cell mates."

"They have nothing to lose: many of them are condemned to death anyway. Murders or unexplained deaths are a regular occurrence," he said.

Rep. Frank Wolf (R-Virginia) said he was "deeply troubled" by the transfer of the pastor.

"With this development – a development without explanation or notice – Pastor Abedini's life is further endangered," he said Nov. 6 in a statement. "Time is of the essence. President Obama and Secretary Kerry must again engage at the highest levels and press in clear and unequivocal terms for the immediate and unconditional release of this innocent man."

"Tehran brutally represses its own people, especially religious minorities including Christians and Baha'is. America always has an obligation to stand with those whose voices have been silenced wherever they may be," said the congressman, who has written a report on religious freedom in the Middle East and south central Asia.

During a phone call with Iran's President Hassan Rouhani in September 2013, U.S. President Barack Obama reportedly urged the pastor's release.

Pastor Abedini's wife, Naghmeh Abedini, voiced deep concern.

"The news of Saeed's transfer to this prison is most difficult to bear. I am devastated and I do not know what to tell my children. I am more concerned now about his safety than at any other time during his imprisonment," she told the American Center for Law and Justice Nov. 5.

"He is truly defenseless in this prison – defenseless from the abuse and violence of other prisoners,  defenseless from a radical government that continues to violate his rights."

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His wife said she is strengthened by her prayers and grateful for the support for her husband and their family.

The American Center for Law and Justice, which is representing the pastor's wife, is calling for continued prayers, as well as efforts to raise awareness of Abedini's plight through social media and an online petition.