Three Christians, including pastor Matthias Haghnejad, have been arrested by Iranian security forces, Christian Solidarity Worldwide (CSW) has confirmed.
Pastor Matthias, from Bandar Anzali, was arrested along with two friends, Mohammad Roghangir and Suroush Saraie, at his home on 5 July at 8.30am. Their current location is not yet known.
Several Bibles were allegedly confiscated from the pastor's house during the arrest, along with pamphlets and a personal computer.
It is not the first time the three have been targeted; Pastor Matthias has already served jail sentences three times, and his two contemporaries were among those arrested in October 2012 during a prayer meeting.
The group were later found guilty of "action against the national security" and "propaganda against the order of the system" and sentenced to prison.
Chief Executive of CSW Mervyn Thomas has said the organisation is "deeply concerned" by the latest developments.
"These men have been targeted by the Iranian authorities in the past, and despite the political charges being levied against them, they were clearly arrested on account of their faith," he said in a statement.
"We urge the Government of Iran to halt its harassment and imprisonment of religious minorities and to uphold freedom of religion or belief, as outlined in covenants to which Iran is party. In addition, the international community must hold Iran to account for the wellbeing of prisoners of conscience."
Iran has a long history of human rights abuses and violence is rapidly escalating across the country, propelled by laws which allow the legal persecution of minority communities such as Christians and Baha'i Muslims, who have been condemned by Iranian authorities as an "illegal cult".
Christian converts are forbidden from praying in public churches and American pastor Saeed Abedini, who is serving an eight year prison sentence for "threatening the security of the state," remains in jail in Iran for his involvement in developing home church communities.