One of seven Christians arrested in a raid on a house church in Iran last month has been released.

Roxana Furughi was released on 1 November after posting bail at $25,000.

She was rounded up along with other members of the Church of Iran in Shiraz on 12 October.

She is the second member of the group to be released, after Bijan Haghighi was released on 25 October after posting bail of a similar amount.

Another two members of the same house church were detained six days later at the Intelligence Ministry's detention centre.

One of them, Ashfar Bahmani, was released 24 hours later. It is believed she was freed on grounds of health.

Christian Solidarity Worldwide said there had been a surge in cases of persecution against Christians in Iran. It fears a concerted campaign is being carried out against Christians of all denominations.

CSW’s Advocacy Director Andrew Johnston welcomed the release of some of the house church members but raised serious concerns over the plight of Christians in Iran.

"Their detention for simply manifesting their faith in communion with others infringes on their religious freedom and contravenes the international covenants to which Iran is a signatory, including the International Covenant on Civil and Political Rights (ICCPR)," he said.

"Moreover, the highly irregular demand of exorbitant bail amounts to secure the release of detained Christians leaves prisoners and their families in uncertainty and financial insecurity.

"We call on the Iranian authorities to end this practice and to release without conditions or delay all who have been detained on account of their faith.”