Christian Solidarity Worldwide (CSW) is calling on Turkey to end discrimination against religious minorities after three Assyrian Christians were arrested on 9 January.
Father Sefer Bileçen, also known as Father Aho, who is caretaker of the 1,500-year-old Mor Yakub Monastery in Mardin province, was among those to be arrested by Turkish Gendarmerie in the Assyrian town of Üçköy.
Also arrested were Assyrian Christians Joseph Yar, chair of the town's council, and Musa Taştekin, from Dibek village.
Taştekin is the only one of the three to have been released so far.
CSW reports that Father Aho was arrested after a member of the People's Defence Forces (HPG) gave a secret testimony.
The HPG is the military wing of the Kurdistan Workers' Party (PKK), which Turkey has called a 'terrorist organisation'.
Father Aho is alleged to have given food and water to members of the HPG at the monastery. His lawyer is contesting his arrest, sources told CSW.
A member of the Assyrian Christian community told CSW: "They accuse us of feeding the PKK when they knock at our doors carrying their guns.
"In the past, PKK fighters killed some community members who refused to give them food as per government's orders. We are caught in a conflict that we have nothing to do with."
CSW's Chief Executive Mervyn Thomas said he was "deeply concerned" by the arrests of the Assyrian Christians.
"We urge the Turkish government to release Father Aho and Mr Joseph Yar immediately, and to allow their lawyers free access to all documents and testimonies related to their case," he said.
"We call on the international community to press the Turkish government to end all forms of discrimination against religious minorities, and to uphold its constitutional obligations to protect and respect the rights of all citizens regardless of their religious affiliation or ethnic background."