Eritrea recently marked 21 years of independence but for Christians in the country belonging to unregistered churches there is little to celebrate.
Members of underground churches report that there are more than 1,000 Christians in prison for their faith.
They have been behind bars for anything from a few months to over a decade.
Some are released with a "stern warning" not to engage in religious activities of the "unregistered" churches, according to Release Eritrea.
One underground church leader said that fellow leaders taken to prison 10 years ago have still not been released and are suffering health problems in prison.
The church leader praised their faith but added that the suffering extended beyond the leaders in prison to their families.
"We praise God when we hear reports of their resolute faith and good spirit. We trust God to safeguard them, but times are tough for their families, their elderly parents are dying and the young children they left behind are now coming of age fatherless," he said.
However, even those who are freed find themselves facing new challenges, having lost their employment. Release Eritrea said it was impossible for former prisoners of faith to find new work "in an economy monopolised by the government that imprisoned them for their faith".
In addition to experiencing poverty, they also face re-arrest. It is little wonder many choose to flee the country after being freed from prison.
But even high level figures are not immune to the persecution. The Orthodox Patriarch Abune Antonios has been under house arrest since 2005 but Release Eritrea partners in Asmara have at least been able to confirm that he is in good spirits and relatively good health, and that he continues to pray earnestly for the church and the people of Eritrea.
"It is hard to comprehend why the Eritrean government is persecuting Christians," Dr Berhane Asmelash, Director of Release Eritrea, said. "This is so barbaric and unacceptable to keep innocent citizens in dungeons for over ten years, and should be strongly condemned by all justice and peace loving people. Please pray for prisoners as well as for the underground church workers."