Last year, Asana, a 14-year-old from Somalia, popped out to get some meat and milk for her mother. As she walked in a Mogadishu market, a car with blacked-out windows pulled up, a door was flung open and she was dragged inside. A man she had never seen before said to the driver: "This is my wife; we just got engaged." The man was Mohamed Dahir, a leader of the terrorist group Al-Shabaab. Her money was taken, she was locked away and forced to become Dahir's wife.

Asana's story is echoed across the globe in a phenomenon that is still little reported or understood. Bride kidnapping, or "bridenapping", happens in at least 17 countries around the world, from China to Mexico to Russia to southern Africa. In each of these lands, there are communities where it is routine for young women and girls to be plucked from their families, raped and forced into marriage. Few continents are not blighted by the practice, yet there is little awareness of these crimes, and few police investigations. The lack of reporting means there are no global statistics, but inquiries over many weeks by The Independent on Sunday have found anecdotal evidence that bridenapping is increasing. Something that belongs more to the Middle Ages is growing in the 21st century.

The lack of awareness, and therefore of any worldwide campaign on the issue, leaves little hope for women such as Asana (her name has been changed to protect her from Al-Shabaab, who still send her death threats). Now 15, and bringing up Dahir's baby son, she considers herself one of the luckier ones. She managed to escape to Kenya after Dahir was killed in a shoot-out. Her story, however, would not be considered "lucky" by many.

Sitting in a plastic chair that dwarfs her childlike frame, she describes her experience: "He beat me and locked me up for one and a half months in a house. He said, 'If you talk I'll kill you'. I was so afraid that I accepted. Even when I wanted to go to the toilet, he escorted me. He wouldn't let me do anything on my own. He also used force to get me to have sex with him; he tied each of my legs with rope so they were apart. It was every night at midnight."

Men such as Dahir are able to get away with the crime in Somalia thanks to a toxic combination of lawlessness, extreme Islamist values that give women no rights, and the shame of lost virginity. Elsewhere, the practice has emerged from a twisting of a traditional culture that has made communities turn a blind eye, allowing it to thrive. In Kyrgyzstan – one of the few places to collect data – the practice has been on the increase since the fall of communism. Some believe this violent subversion of a tradition (which was historically for show and done with the consent of the wife) has become popular to avoid the embarrassment of being unable to afford a dowry.

Up to a third of all ethnic Kyrgyz women in Kyrgyzstan are kidnapped brides, and some studies suggest that, in certain regions, the rates of bride kidnapping account for up to 80 per cent of marriages. In six villages scrutinised for a recent survey, almost half of the 1,322 marriages registered were from bride kidnapping, and up to two-thirds were non-consensual. Earlier this year, two 20-year-old students committed suicide after falling victim to bridenapping. The deaths of Venera Kasymalieva and Nurzat Kalykova prompted demonstrations in their home province of Issyk-Kul, but little has changed.

Despite bridenapping being a criminal offence carrying a maximum three-year jail term, very few cases are brought, and most of those who are prosecuted get away with a negligible fine. "Once bride kidnapping was characteristic mostly in rural areas, but it has become widespread everywhere, including the capital, Bishkek," says Gazbubu Babayarova, founder of the Kyz Korgon Institute, an organisation that campaigns to eliminate bridenapping in Kyrgyzstan.

Most people in Kyrgyzstan view the practice as a tradition rather than a crime. There is such a thing as "consensual" bridenapping, where the bride agrees to be taken as part of a custom, but a more violent version of this "tradition" has grown in the 21st century. Russell Kleinbach, a professor at Philadelphia University who is an expert on the issue, believes it is only since the 1950s that this tradition has morphed into something that is widespread, brutal and non-consensual.

Ms Babayarova is herself an example of how this custom has spread to urban, educated Kyrgyz communities. Seven years ago, she was kidnapped by one of her closest friends, who was a medical student. He did not accept her protestations that she did not want anything more than friendship and entered into an arrangement with both their parents to kidnap her.

Early one morning he stopped by her house in Bishkek with a friend and offered to give her a lift to work in his car. Instead of driving to her office, the car veered off in another direction. When she asked what was going on, they just laughed. "I felt that I was like a fish caught in a net. I was horrified, worried and very angry," Ms Babayarova recalls. Soon she arrived at his home in a small village, where around seven of his female family members were waiting for her, including both grandmothers.

She was only able to escape after promising to marry him the following autumn. When she got home – with no intention of marrying him – her own family started to telephone her, saying she had brought shame on them for abandoning the deal.

Nearby in Muslim Chechnya, the region's leader, Ramzan Kadyrov, gave a powerful speech last year urging his followers to "eradicate" the age-old practice. "I declare ... that we will root out once and for all from our society the kidnapping of young women," he said. Sadly, that promise has not been kept. Though bridenapping is outlawed under the Russian legal system, it is still widely practiced in the region.

A shortage of women in China, blamed on people having sex-specific abortions because of the one-child policy, has resulted in men being willing to go to extreme lengths to find a wife. Future grooms pay kidnappers between £120 and £500 to find them a bride. Dealers in wives will often go to Vietnam, where women are a less scarce commodity, capture young women, and smuggle them across the border to their new Chinese "husbands".

This violent practice is also spoken of as a tradition outside Asia and Africa. Among the Tzeltal community in Chiapas, southern Mexico, women are routinely kidnapped for marriage. Often this is by men who have failed to find a mate. It is customary for such men to go out and capture a woman with the help of their friends, take her to the mountains, rape her, and hold her there. Once the girl's father's anger is believed to have subsided, the kidnapper will come down from the mountains with his prize and "buy" her with traditional gifts of rum.

If a girl in her late teens or early twenties walks alone in the pastoral area of Umutara in Rwanda, and is caught unawares, she risks being raped and beaten by gangs of youths who aim to break her resistance so she will marry a boy who has chosen her. The boy in question will then spend several nights with her – by which point she will be considered too tainted to marry anyone else. After this, the young man will go to a ceremonial meeting with her family to apologise for having "stolen" their daughter – a ceremony which usually ends in his getting her hand in marriage.

The United Nations has been aware of stories like Asana's and Ms Babayarova's – not to mention ones with much more tragic endings – for decades, but admits that little has been done to tackle it. Aminata Touré, chief of the Gender, Human Rights and Culture branch of the UN Population Fund, said: "What we really need is more research to come up with the level of the problem. For something to be registered as a crime, it has to be reported; that's the problem, because it's often seen as a cultural practice and not a crime. When it's not perceived as a crime, it becomes even harder for this practice to be registered as one.