A pastor imprisoned in Iran for his faith is recovering in hospital after surgery to treat stomach ulcers and colon complications.

Christian Solidarity Worldwide (CSW) said it had received reports that the operation on Pastor Behnam Irani was successful and he will be returning to Ghezal Hesar Prison on Tuesday.

The medical problems caused severe bleeding and at one point the pastor lost consciousness.

While it welcomed the surgery, CSW criticised the prison authorities for failing to have Pastor Irani treated sooner. 

Pastor Irani was the leader of a Church of Iran congregation before his imprisonment.  Since 2006, he has been in and out of prison because of his faith.

He was first arrested for crimes against the state in December 2006 and released on bail the following month.

He was arrested again on the same charges in 2008 and given a five-year suspended prison sentence, meaning he was free to go.

However, this was not to be the end of Pastor Irani's woes as in April 2010, he was detained following a raid on a house church service and forced to spend two months in prison.

In January 2011, he was again imprisoned for a year for crimes against the state and shortly before his release, was informed he would have to serve the five-year suspended sentence from 2008.

CSW reports that Pastor Irani has been subjected to psychological torture during his time at Ghezal Hesar prison. In the first few months, he was held in isolation in a small cell and repeatedly woken from sleep.

He was then moved to a cramped room where inmates could not lie down to sleep and was finally transferred to what CSW described as a crowded, filthy cell.

According to the organisation, many of the 40 criminals who share the cell are violent.

He has also suffered "regular" beatings from cell mates and prison authorities, as well as death threats.

CSW chief executive Mervyn Thomas said: "While we are pleased to hear that Pastor Irani is recovering well in hospital, it is unacceptable that his condition was allowed to deteriorate to such an extent before he was given appropriate treatment.

"We continue to call for his release from prison. Although he was convicted on political charges, in reality he is in prison on account of his faith and in contravention of the International Covenant on Civil and Political Rights, to which Iran is party."