For many Pakistani Muslims, visiting a shrine and donating money to beggars go hand in hand. But their generosity has encouraged the creation of a "begging mafia" which forces thousands of children into a life of slavery.

Shrines dedicated to holy men are dotted across most cities and towns in Pakistan. In the folk Islam of the region, they are regarded as saints, and can attract huge numbers of worshippers, eager to pray for their blessings.

The shrines have always been a magnet for beggars, especially children, as many of the pilgrims believe giving money to the poor will increase the chance of their prayers being heard.

The result? Children are being kidnapped and traded between begging gangs, says Mohammed Ali, founder of the Roshni Helpline charity.

"In 2010, 3,000 children went missing in Karachi alone," says Ali.

"Many of these children will be moved around shrines in Pakistan. They will have their heads shaved. They will be tattooed. They will be made unrecognisable to their parents.

"The culture of begging at shrines is so prevalent that the police will rarely intervene or ask children how they got to a shrine."

A few hours spent at any shrine in Pakistan will reveal that the beggars with the most pronounced disabilities attract the most attention and, in turn, the most money.

In some cases, if a child isn't disabled, a disability can be inflicted upon them, says Ali.

Find out more Mice, Mullahs and the Begging Mafia is an episode of the programme Heart and Soul. It broadcasts on the BBC World Service at 19:32 on Saturday 1 June, with several repeats. For details, see the website.

"We have dealt with cases where children have a limb cut off," he says. "Their hair can be pulled out. An eye can be removed. The intention is for the child to attract sympathy and money."

But children with existing disabilities are also sought after by kidnappers.

An hour outside Karachi, in the town of Hyderabad, lives taxi driver Mir Mohammed, with his wife and three children.

His eldest son, Mumtaz, recently went missing.

"He is disabled. I used to do everything for him. He was in his wheelchair just down the road but then we couldn't find him," says Mohammed.

"Some people say they saw him being forced into a rickshaw. It must have been the begging gangs. A boy like Mumtaz is precious to the gangs. We have been searching all the shrines, but we can't find him. We want him home. We are desperate."

Roshni Helpline workers are circulating Mumtaz's photograph at shrines and the police will be asked to look for him. But the scale of the problem and the sheer number of shrines across Pakistan means that many missing children will never be found.

There is nothing Islamic about leaving your child at a shrine or donating money to a child who is being forced to stand in front of a shrine Mohammed Ali, Roshni Helpline

One of the best-known shrines is home to the tomb of Saint Doley Shah in Gujrat.

It is the town's focal point and attracts visitors from across the Punjab, especially women praying for fertility. It is also the historical home to the Doley Shah's "chooay" or "mice" - people with a genetic defect which causes a shrunken skull.

They were believed to be blessed and attracted donations from almost every visitor, though now there is only one left, a woman who is fed, clothed and looked after by the shrine committee, not by the mafia.

Everyone who visits the tomb is familiar with the shrine's legend.

"If you are barren and you pray at the shrine, the Saint will grant you a child but it could look like a mouse," one visitor told me.

"You have to donate that child to the shrine or all your future children will look like mice too."

According to geneticist Dr Qasim Mehdi, Pakistan has a high rate of genetic disease, resulting from "an extremely high percentage of cousin marriage". In the past, he says, it was common for parents to leave a disabled child at a shrine - a tradition not confined to Gujrat.

The practice has now been banned, and abandoned children have become rare.

"But the number of begging children has not gone down," Mehdi says. Instead, he argues, abandoned children have been replaced by kidnapped children.

Pakistan needs to undergo a "culture shift" to remove the financial reward for exploitation, he suggests.

"People who visit shrines are still willing to hand over money without asking any questions," he says, "either about where their donation is going and how the person asking for the money came to be at the shrine."

Mohammed Ali at the Roshni Helpline is eager to set this culture shift in motion, by stimulating public discussion.

"Criminal gangs need to be tackled by the police but the biggest problem is superstition," he says.

"We need to teach people that there is nothing Islamic about leaving your child at a shrine or donating money to a child who is being forced to stand in front of a shrine.

"We need to ask more questions and think about where these children are coming from. Only then will this problem be solved."

Mice, Mullahs and the Begging Mafia is an episode of the programme Heart and Soul. It first broadcasts on the BBC World Service at 19:32 on Saturday 1 June. Details of repeats are available via the programme's website.

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