Christians in Afghanistan are leaving the cities in a bid to evade the Taliban, according to partners of Release International.
With borders to neighbouring countries closed, Afghan Christians have been unable to leave the country. Instead they have fled to its remote regions as the Taliban cracks down on dissenters and opponents.
The Taliban regard Christians as apostates and therefore worthy of death. Many of them are in hiding and Release International says some have received death threats.
Even before the fall of Afghanistan to the Taliban, the country's Christians lived with persecution, but Release CEO Paul Robinson says this bitter experience may have set them in good stead for the worsening climate.
"The one good thing we can say about this is that the underground Church is increasingly well-equipped to weather the storm," he said.
"The Church is invisible and it has already learned how to operate underground."
Release International has been partnering with other organisations to provide Christian literature, digital discipleship material and broadcasts to encourage and equip believers in Afghanistan and neighbouring countries.
"Support and encouragement through the airwaves, whether by radio, satellite television or social media, has never been more needed than it is today," said Mr Robinson.
"The Church is having to learn to operate much as the early Church in the book of Acts – under the continual threat of persecution."
While the threat is real, Release has also voiced concern that some reporting is distorting the picture.
This includes a 2009 rumour of missionaries about to be executed in Iraq that was recently shared on social media with the claim that it was happening in Afghanistan after the country's fall in August. The post went viral.
"Understandably, there is a great deal of fear and rumour," said Mr Robinson.
"This is why we talk to partners who are working directly with the underground church."
One of its partners in the region is Christian media ministry SAT-7 Pars, which broadcasts faith-based programmes into the country by satellite.
The ministry said it had received many messages from desperate Christians trapped in Afghanistan.
One caller sent in a prayer request saying: "Oh Lord God, please protect us, because we are facing hell."
Another said: "My family and I came to Christ two years ago. I and my family have received death threats. I have no other way but to escape from the country. Help us to be heard so we can flee from this hell."
One heartbreaking message read: "The terrorists are in the process of occupying us, demolishing what we own. Where can we go? What can we do? Please continue to pray for us."
SAT-7 Pars executive director, Panayiotis Keenan, told Release International: "Since the Taliban has taken over, we are receiving many messages from Afghanistan that the persecution is getting harder.
"Afghan Christians are contacting us on a daily basis, describing how difficult the situation is. They are hiding and meeting in secret locations. But winter is coming and that will soon become more and more difficult."
Release welcomed the UK government pledge to take in 20,000 Afghan refugees - with the priority going to women, children and those at risk of persecution - but it expressed concern over plans to clamp down on refugees entering the UK by unauthorised routes.
Mr Robinson called on the UK government to provide a place of welcome for those forced to flee persecution.
"Increasing numbers of Christians around the world are having to flee in the face of extremism," he said.
"We are pleased to see the UK government is prioritising Afghan refugees who are facing persecution.
"Let us continue to do all we can as a country to support those who have been uprooted from their homes because of their faith. They need our welcome and support."