Warning: Some readers may find some of these details upsetting

Rusul woke to find herself alone. Her new husband had gone. The marriage had lasted just three hours.

It wasn't the teenager's first marriage. It wasn't even her second, third or fourth. In fact she's been married too many times for her to count.

Rusul's harrowing way of life was triggered by an encounter when she was at work.

She would watch as girls not much older than her in tight clothing and bright make-up came in to wait expectantly. Older men would soon come in to pick them up.

“They were such beautiful young girls, I couldn't understand why any girl would sell herself like this,” she says.

She herself was also vulnerable - estranged from her family and supporting her sister Rula.

But despite her hardships, she had made a promise to herself that she wouldn't depend on a man for survival. When men sneaked their number into her hand, she always ignored them.

One day, a man came in to her workplace and started chatting to Rusul. They talked about her past, about why she was working, rather than in school, and where she was from. She felt he actually cared.

Life had become increasingly tough for Rusul. Living in Baghdad on her meagre salary was a struggle.

Despite her initial vow to remain independent, she found herself dreaming of a husband - one who would take care of them both.

The man would come to her place of work every day to do what he could to grab her attention. Rusul gradually developed feelings for him.

After just a few weeks, he proposed. He took her to Kadhimiya in Baghdad. As they walked into a religious marriage office, Rusul felt a flutter of excitement.

The ceremony itself was brief - the cleric recited a few words, asked her whether she agreed with the $250 [£200] dowry she would receive and presented her with the contract. Rusul couldn’t read, but even if she could she might not have realised anything was amiss.

Within minutes of the cleric's blessing, her new husband had taken her to a nearby apartment in an apparent rush to consummate their marriage. Although Rusul was nervous, she was looking forward to finally having a proper home for her and her sister. She followed her husband into the bedroom and, as she closed the door behind her, prayed that this man would treat her well, that their life together would last.

And indeed the first few days seemed like a fairy tale to Rusul.

“I felt like a weight had been lifted off my shoulders. Finally, I didn't have to provide everything,” she says.

But after just a few weeks her husband disappeared.

Little did Rusul know that their marriage had an end-date before it had even begun. It was a special type of Islamic marriage - a “zawaj al-mutaa” or “pleasure marriage” - and that it was a way of allowing religiously approved sex. Hers had now expired.

She decided to visit the cleric who married them. She says he seemed to be expecting her.

Mutaa marriages are derived from pre-Islamic tradition in both Iran and Arabia. Today they are sanctioned by Shia clerics in Iraq and neighbouring Iran, where most Shia adhere to what is known as Twelver Shiism.

Experts say that under Shia Islam the object of such marriages is sexual enjoyment and not procreation, and that in previous centuries they took place mostly at pilgrimage sites and trade centres, where lonely men travelling long distances often sought company.

A mutaa marriage is subject to a contract that specifies its length and the amount of compensation given to the temporary wife. But the contract can just be verbal, and a cleric - though often present - is not necessary to validate it.

It can last from an hour to 99 years. The man is not obliged to provide daily maintenance and has the right to end the contract at any time.

Mutaa marriages are not permitted under Sunni Islam. But some Sunni clerics sanction alternative variants of marriage, such as “misyar”, which some experts say performs a similar function to mutaa marriage and has also been criticised as exploitative of women.

Supporters of mutaa marriages say they can be a positive move for couples who are aware of what they are doing. But their temporary form means they are also ripe for exploitation.

In the case of girls like Rusul, they essentially enable child abuse. They are also not recognised under Iraqi civil law. The criminal code states that any person who has sex outside of marriage with a girl or a woman could be punished with up to seven years’ imprisonment if she is between 15 and 18, or up to 10 years if she is under 15.

Rusul says the cleric now suggested she simply continue to enter into more mutaa marriages, arguing that she had no other choice given her difficulties.

He took photos of her.

Rusul knew she would struggle to survive for much longer on her salary, and that her lack of education afforded her little prospect of a better job. She also knew that the fact that she wasn't a virgin would make it difficult for her to find a man who wanted a permanent marriage.

“The cleric became a middle man, giving me work, and I had no choice but to follow that road,” she says.

She won't go into details about how much she earns but says the cleric takes a fee from the client and then pays her the dowry. She says the length of her contracts have varied from a few hours to several weeks.

“When the Sheikh [cleric] calls up and says, 'I've found someone suitable for you,' I can't say no.”

Rusul has by now slept with dozens of men - so many that she has lost count - in the course of these mutaa marriages.

She says the cleric provides her with contraceptive injections to ensure she doesn't get pregnant.

“This is something that is very widespread. There are many girls like me.”

Kadhimiya

Kadhimiya is the location of one of Shia Islam's most important pilgrimage sites. Millions of people come from all over the world to visit the mosque commemorating the martyrdom of the death, in the 8th Century, of Moussa al-Kadhim, the seventh of the 12 Shia imams.

Dotted among the bustling market stalls surrounding the shrine are dozens of offices where couples go to get married under Islamic law, or Sharia, before appearing before a judge to obtain an official marriage certificate. Most couples are seeking permanent marriages. But some are looking for mutaa marriages.

Despite being illegal in Iraq, the BBC found that mutaa marriages were widely available in Kadhimiya. Out of 10 clerics approached by a BBC undercover reporter, eight said they performed them. Of those eight, we had further conversations with two who agreed to approve them for girls as young as nine.

It is impossible to quantify exactly how widespread the practice of under-age mutaa marriage is in Iraq.

Ghaith Tamimi, a former senior Shia cleric from Karbala, said he witnessed thousands of mutaa marriages but none with children. He acknowledged that Sunnis also enter into informal marriages, but said the fact that the Shia clerics are closer to those in power means they can act with impunity.

The BBC decided to investigate after it was contacted by concerned members of communities in Iraq.

In the marriage offices in Kadhimiya, clerics approached by the BBC undercover reporter elaborated on their practice.

“You can marry a woman for half an hour, and as soon as it's over, straight away you can marry another one,” says one of these clerics, Sayyed Raad, who uses the honorific title of Sayyed because he claims descent from the Prophet Muhammad.

He also says he can arrange a “first class” hotel suite for the reporter and his mutaa marriage bride, despite it being illegal for a couple to rent a hotel room in Iraq unless they are married under civil law.

Some of the clerics also appear unconcerned that the bride in question is very young.

The legal age for marriage in Iraq is 18, although judges are allowed to permit girls as young as 15 to marry in “urgent” cases. Sharia, meanwhile, says that girls are allowed to marry once they have gone through puberty.

Clerics are required by Sharia to obtain parental consent if the girl is under-age. But Sayyed Raad is happy to officiate even when our reporter pretends the girl in question is a 13-year-old virgin.

Instead he just advises against taking the girl's virginity. He suggests anal sex as an alternative. And he is happy to conduct the ceremony over the phone, with the girl not even present.

He charges our undercover reporter $200 for the minutes-long ceremony.

He even agrees to procure our reporter another girl for a later date.

“I can take a photo of her and send you her photo. Then you agree with her. Then when you come back she's yours.”

Sayyed Raad brings another young woman available for mutaa marriage to meet our undercover reporter. The cleric says she is available to spend the night with him for $300. When the reporter says he doesn't want to go ahead with the mutaa marriage, Sayyed Raad then offers to use her to find the reporter a younger bride.

“Maybe she can find me a girl who is 14, 15, 16 years old. I will go with her to check the girl and if she's young I will bring her to you.”

In Karbala, a Shia holy city 120km [75 miles] south of Baghdad, the BBC asks Sheikh Emad Alassady, the most senior cleric in the city's Sharia marriage office in Karbala mosque, whether he approves of the practice of mutaa marriage. He says although allowed in Sharia he would never officiate one.

“The culprit would be sentenced to prison, even if he was a cleric” he says.

But in the streets around the shrine, some clerics are giving very different advice.

Cleric Sayyed Mustafa Salawi says he would be happy to officiate a mutaa marriage between the reporter and a girl the reporter pretends is 12 years old. He is not concerned that the bride is young.

“Nine years-old plus, there's no problem at all. According to Sharia, there is no problem... Do what you desire.”

And when contacted again, a few days later, to find out if he could provide another bride, he is happy to provide a choice of women.

“They won't send photos but when you see them face to face, they're good girls, beautiful girls. If you don't like her, there will be a second and a third and so on.”

The BBC later approached the clerics it had filmed undercover to ask for their response. Sayyed Raad denied he performed mutaa marriages at all. The others did not respond.

Sayyed Raad had said he was a follower of Grand Ayatollah Ali Sistani, Iraq's most influential Shia cleric.

The BBC approached Ayatollah Sistani's office in the holy city of Najaf with the reporter’s evidence, and asked him to clarify his stance on mutaa marriages.

“If these practices are happening in the way you are saying then we condemn them unreservedly,” his office says in a statement. “Temporary marriage is not allowed as a tool to sell sex in a way that belittles the dignity and humanity of women.

“A guardian of a girl should not permit her marriage without her consent… and she is not supposed to marry if it’s against the law, which could bring troubles to her.”

Like some other Shia leaders in Iraq, the 89-year-old Ayatollah Sistani has in the past - in a book published 25 years ago called The Path of the Righteous - written that if a child under nine were promised in marriage or temporary marriage, sexual touching was religiously permitted.

In the statement to the BBC, the ayatollah’s office said: “times had changed and it had been erased from his current books”.

Ali, a professional man in his 40s, is one of those who uses clerics to source him women and girls for mutaa marriages. “It doesn't count as a sin. It is available and it is cheap and it's fine to do it,” he says.

“Lots of clerics do [facilitate] it, but I only use two because they provide me with all the girls I need,” he says.

“The cleric has a photo album, sometimes several girls are sitting in his office. If you like one of them, you can take her. If you don't, your second choice is the photo album.”

Ali says he personally prefers girls who are 16 and older because they are more experienced and more affordable than the younger girls. The 12-year-olds, he says, are “fresh” and therefore more expensive, earning the clerics as much as $800 per contract.

Rusul agrees it is the virgins that are in demand.

“There are clerics who look for young virgin girls because many customers want them, they are more desired, and people pay more for them. This is happening to many girls - not just a few.”

She says 20 is the cut-off age for girls working for the clerics.

Losing your virginity outside marriage carries considerable risk in the country, as it is seen by some Iraqis as tainting family honour.

Mona was just 14 when she was persuaded into a mutaa marriage with an older man who followed her home from school.

Now several years older, Mona is under pressure from her family to marry, and is terrified her future husband will find out she's no longer a virgin. She says that her uncle killed her cousin just for having a boyfriend. She says she is contemplating suicide.

“I have no way out. If I feel under any more pressure, I will do it,” she says.

Since the BBC spoke to Mona, she has run away from home.

But it's not just girls who are vulnerable to the potentially exploitative tool of mutaa marriages.

Rana, in her 20s, was divorced by her husband after she fled to Baghdad five years ago, after militants from the Sunni jihadist group Islamic State [IS] overran her home city.

When she met someone else she was delighted by his proposal. She had assumed it would be a permanent union. She didn't bother to read the contract because she trusted her husband.

Even if she had, she might well have missed the fact that it was a mutaa marriage, since the contract is the same as a regular Sharia marriage contract - the cleric just writes “mutaa” in brackets, a detail that is easy to miss.

“We had three of the happiest days of my life - ordering food. He cherished me. When you're broken, and someone comes and gives you hope, it's very precious.”

But then her husband took her out shopping, and without warning vanished.

When her family discovered that her marriage had only been temporary, they rejected her. Although mutaa marriages are sanctioned by Shia clerics, it's seen as dishonourable - essentially prostitution - by many sectors of Iraqi society, both Shia and Sunni.

“When you get married, you feel secure, you're happy. He's your husband, you believe you have a future, but it turned out it was all a lie. For us, a cleric is something very special, but then you discover that this guy wearing a turban is a cheat.”

Some clerics defend mutaa marriage as a way for widows and divorcees to obtain an income, as the woman gets a dowry. They also say that women have sexual desires and want a religiously-approved means of sleeping with men.

Rusul says this is a false notion.

“Maybe some desire this, but I don't think many people would like to take that road if they are financially secure. Why would a teenager want to do this?”

Ayatollah Sistani’s office told the BBC the abuses we have witnessed are because the authorities are not enforcing the law.

An Iraqi government spokesman told the corporation that it is difficult for the authorities to act “if women don’t go to the police with their complaints against clerics”.

But for girls like Mona, who don’t want their families to find out about their mutaa marriages, going to the police seems impossible.

There are no statistics for how many mutaa marriages are being conducted but anecdotal evidence suggests they have become more common in the wake of the US-led invasion of Iraq in 2003.

The invasion toppled Saddam Hussein's nominally secular government, and ended the political and economic dominance of Iraq's Sunni minority and the persecution of the country's Shia majority. Since then, Iraqi Shias have sought redress and reversed the imbalance of power. The country's Shia clerical establishment now holds enormous sway.

Though it isn't possible to verify all the details of Rusul's story, sources have confirmed that many elements of her account are similar to those of other girls who have been exploited by clerics in this way. Other girls, for example, have spoken of being given contraceptive injections.

Rusul regrets the day she ever unwittingly took this path.

“The moment a girl starts doing this, her life is ruined.”

The courthouse

Unlike mutaa marriages, permanent Sharia marriages are not outlawed in Iraq, though they do need to be signed off by a judge if they are to be officially recognised.

But like mutaa marriages, they can also put vulnerable girls at risk if the civil legal system is bypassed.

One cleric says that under Sharia, the bride must simply be able to “handle the sex. Sometimes that would be 10 years [old]”.

Marrying off their daughters at a young age is tempting for parents struggling to look after them. “Girls are seen as a financial burden,” says Yanar Mohammed, president of the Organization of Women's Freedom.

In addition, many conservative parents marry off their girls early to safeguard or protect their reputation, by ensuring they do not mix with men or take boyfriends - which in conservative communities jeopardises the honour of the girl and her family.

But at the point at which permanent Sharia marriages are signed off by a court - necessary for example to allow couples’ babies to be delivered in hospital - Iraq’s law on the minimum age for marriage should be enforced.

Some of the country's judiciary, though, don't seem to be enforcing the law with any enthusiasm.

At Sadr City courthouse, couples gather with their parents to have their permanent Sharia marriages signed off by a judge.

One of them, Haneen, is just 13. A cleric married Haneen to her husband in a permanent Sharia marriage six months ago, and now she's pregnant.

Because she was under-age when she got married, her father and groom could get two years in prison. Instead they are fined just $50.

The judge in the case defends his position.

“The marriage of minors can sometimes be to their advantage, she's agreed to it and wants it. As you know, marriage is a fact of life.”

There is a queue of fathers waiting for their daughters to get married before the judge.

One of them, Sami Okaybi, is with his 14-year-old daughter.

“Our young men aren't even interested in 18-year-olds,” he says. “They're looking for 13-, 14-, 15-year-olds. At 18 she will barely have a chance.”

The court's social worker says she has processed 126 teenage marriages in the last six weeks alone. She predicts most of them will end in divorce, just as Rusul's first marriage did.

“Only four or five will be successful,” she says, explaining that such young people cannot handle the responsibility of marriage.

The social stigma attached to divorce in Iraq is significant. A divorced girl or woman can be rejected by her family.

This leaves her extremely exposed, says Yanar Mohammed.

“If you are a divorced woman you do not have a future, you are looked at as a tainted person.

“Once you have reached that situation you are very vulnerable to the cleric who whispers in your ear that they have the solution.”

When Rusul talks about her sister, her face lights up. Rula’s life has so far not taken the same path as Rusul’s, and she is determined that their lives remain very different.

“She is on my mind the whole time, but I am trying to protect her,” Rusul says.

“I think she will do very well. She will be the one that saves me from this life.”

Some names have been changed to protect the contributors' identities.