Women with ties to Isis are raising funds among sympathisers in Britain and other European countries to help them flee detention camps in Syria.

An investigation by The Sunday Times has uncovered details of how people in the UK have donated to, and promoted, an international crowdfunding operation reliant on an encrypted messaging app to funnel money to Syria and pay people-smugglers to spirit women and children out of the camps.

Some of the fundraising originates in the camps, where thousands of inmates endure squalid conditions but have access to mobile telephones they use to post appeals on social media.

These are then “shared” by sympathisers around the world — including in the UK. One Muslim woman living in northern England shared a post dozens of times appealing for funds to free “sisters” in Syria.

Europe is a vital component of the fundraising effort. Several hundred European women, many of them wives of killed or imprisoned Isis combatants, are among the detainees, many of them desperate to escape. These include dozens of British women and children, among them Shamima Begum, who left the UK aged 15 to become an “Isis bride” and who has since been stripped of her British citizenship.

Donations follow a circuitous route in cyber-space through various intermediaries before ending up in the hands of Isis women hoping to flee or of the smugglers helping them. An undercover reporter was told last week by a fundraiser that any donation would go to Germany first before being sent to the camps. Three middlemen claimed that many donations had been made from Britain.

France, too, is involved — police there detained 29 people suspected of involvement in fundraising for women in the camps; and in Holland a convicted terrorist known only as Samir A was accused in court last month of helping 12 women on a Dutch watchlist to escape from the camps.

The first step in the process is for would-be escapees, parroting the vivid language of professional humanitarian fundraising appeals, to post testimonies on Facebook complaining of beatings, strip searches and squalid camp conditions from mouldy bread to water shortages and lack of healthcare and sanitation.

“Now imagine you have small children with you in this room experiencing the same thing, with the enemy showing no mercy,” one of the women wrote recently in her appeal for funds. “In fact, they [the guards] enjoy seeing your suffering, weakness and helplessness. You are hit in the face, beaten and strip-searched in front of your children, while they cry and scream, unable to understand.”

Testimonies typically are followed by a “how to help” guide, including details of an account on the encrypted Telegram messaging app. Would-be donors are urged to make contact with the account. Once connected, they are invited to send whatever they can afford.

Funds are then transferred to a middleman, who either passes it to a “broker” in the camp — who gives it to the women hoping to escape — or sends it directly to a smuggler in Idlib. Smugglers then bribe camp guards and organise transport to Idlib or another rebel-held part of Syria.

The women often have to change cars — and even smugglers — several times before reaching their destination. This may help to explain the exorbitant going rate: between $10,000 and $15,000 for a woman and three children. “So if 10 people send $1,000 each, we will reach the goal. Or if 20 people give $500 each, we will reach it as well,” wrote one Facebook user, apparently a woman in one of the camps. “Free your sisters from the camps — SPREAD THE WORD.”

The use of people smugglers is not without risk, however. Some women have complained on social media of being scammed: sometimes the smuggler takes the money and runs.

An undercover reporter who made contact with various Telegram accounts was told to transfer funds using the untraceable bitcoin cryptocurrency.

“It’s easy,” wrote the intermediary. “You buy the bitcoins and, once you have them, you send them.” The message went on: “There is no trace, many brothers and sisters did it, alhamdulillah [God be praised] there is no problem with it and this way is used since a very long time, the authorities of your country has no proof against you using that way.” Another Telegram intermediary wrote: “May Allah reward you for your interest to help the sisters in need.”

Several intermediaries offered to provide photographic proof of the money being delivered to women in the camps. One recommended sending money over the PayPal internet purchasing system and labelling the transaction “something stupid like a birthday gift”.

European camp inmates regularly post pictures of hand-made signs soliciting donations and confirming that various middlemen are working on their behalf. They also publish pictures of food — chocolate bars and biscuits — that they say has been bought with donations from abroad.

“I may not be your wife or your mother or your daughter, but i am YOUR SISTER in islam!!” wrote one woman. She added: “Sisters have been imprisoned for YEARS … have you forgotten us? What’s the matter with you!! FEAR ALLAH, wake up!”

At least one British woman claims to have been smuggled out of a camp. In a recent Facebook video a woman calling herself Maryam Al Britaniya “from UK” pleads with followers to send money.

Most of the Europeans, including British women and about 60 children, are held in two camps run by a Kurdish-led militia.

One of the camps, Roj, where Begum is held, is tightly guarded but the other, Hol, is too big, say guards, to police properly: a sprawling tent city that is home to tens of thousands of people, a mix of former Isis camp followers and Iraqi and Syrian refugees.

Few of the British women are thought to hold out much hope of being allowed to return home through legal channels. They can only hope to find some other way out of the camps.

While some inmates have been smuggled out, others are caught trying to flee. British sisters Salma and Zahra Halane — nicknamed the “terror twins” after dropping out of school near Manchester to join the caliphate in 2014 — were intercepted by Kurdish-led forces while attempting to escape the more heavily guarded Roj camp.

Successful escapes from Hol, by contrast, are more common. “You can bribe the guards there,” said Vera Mironova, a research fellow at Harvard University who is in close contact with several women held in the Syrian camps. “There are so many women fundraising to get out.”

Some of those lucky enough to escape make their way across the border to Turkey — and from there to other countries under false identities. Others have been caught by Turkish authorities and imprisoned or deported.

Last year Tooba Gondal, a former London university student known as the “Isis matchmaker” escaped from a camp. She was sent to France after being detained in Turkey.

“Some of them buy documents in Istanbul and go,” Mironova said. “I know one Russian who made it to Germany. If Russians managed to do it, why not Europeans?”

Despite the difficulties involved, some women try to escape with their children. In one post, a grandmother from the Maldives calling herself Umm Abdallah asked for donations to help her flee the camp along with her two daughters, three orphaned grandchildren and two other orphans.

“Since this is a big family, the expense needed for this is more,” she wrote. “Oh my brothers and sisters, in order to free my family, please help us with any amount possible. Even if it’s by giving 1$. And do you not wish to free yourself from the hellfire by spending a little more in the cause of Allah?”