Saeed Abedini has been released after three and a half years in prison, as part of a prisoner swap with the United States.

Saeed was released alongside three fellow Iranian-Americans: Nosratollah Khosravi-Roodsari, Amir Hekmati and Jason Rezaian.

Tehran prosecutor Abbas Jafari Dolatabadi confirmed the news, saying: “In line with the approvals of the Supreme National Security Council of Iran and the general interests of the regime, four Iranian dual nationals were released today in the framework of the prisoner exchange.”

The news of the release of the four dual national prisoners comes as the implementation of the Iranian nuclear deal in Vienna is expected to be announced in the next few hours in the presence of the Iranian and US secretaries of state.

The release of these dual nationals is part of an agreement between Iran and the United States to exchange prisoners. Twelve Iranians are being held in the United States on charges of “circumventing sanctions” and seven are said to be set to be released.

Saeed was serving an eight-year prison sentence for “setting up house churches in order to disturb the security of the country” and “collusion to commit a crime”. He said that during his interrogations he’d also been threatened with death.

He was arrested in September 2012 while on a visit from his home in America to Iran, where he was seeking to establish an orphanage.

He was first sentenced to death in the early winter of 2012, but after an appeal was sentenced to eight years in prison by Judge Pir-Abassi of Branch 26 of the Islamic Revolutionary Court in Tehran, in January 2013. His appeal was later rejected by Branch 36 of the Court of Appeals in Tehran.

Saeed, who is 34 years old, has been suffering from urinary tract and kidney disease. He began his sentence in Tehran’s Evin Prison, but was later transferred to Rajaei Shahr Prison in Karaj.

His wife, Naghmeh, has spoken out against the mistreatment of her husband in prison, saying he has been repeatedly beaten during interrogations and that he suffered internal bleeding but was denied treatment.

Iran is 9th on the Open Doors’ World Watch List of the 50 countries where it is most difficult to be a Christian. Iran’s ranking in this list has dropped from seventh in 2014 to ninth in 2015, despite the worsening situation of violation of religious freedoms in the country. The reason for the decline is the unprecedented escalation of anti-Christian actions in other countries in the Middle East and North Africa.

Christian converts in Iran continue to be arrested and given prison sentences simply as a result of their religious activities. There are currently at least 103 Christians in prison in Iran.