Every night hundreds of women sell their bodies for sex in darkened brothels in El Mina, a poor district of the Mauritanian capital Nouakchott. For them it is a means of survival, but for others facilitating this illegal trade it is big business.
It is well past midnight and the occasional bare light bulb hanging in a doorway provides sparse illumination, making it difficult to negotiate the rubbish and uneven sandy ground underfoot.
"At the brothel, we try to keep a low profile. We use only candles so as not to draw attention to the place," explains Janine, a rotund 48-year-old sex worker from Senegal.
Janine won't meet at the house where she works. And Janine is not even her real name. But she has agreed to talk about her secret life in the shabby back room of a telephone call centre.
Prostitution and all activities relating to it are illegal in the Islamic Republic of Mauritania. Women caught selling their bodies for sex can be sent to jail for up to three years. It is even a crime to live with someone who is habitually involved in the trade.
Prosecutions are rare, but police harassment is constant.
The sex workers of El Mina say the police are more interested in extorting money from them than in enforcing the law.
"The only problem I have working in Mauritania is with the police," Janine said. "I service all sorts of men at the brothel and have no problems, but when the police come they take everything that everyone has."
Janine had trudged through a maze of dark narrow backstreets to reach the call centre. She is originally from Casamance in southern Senegal and her clothes - bright thick cottons with wrapper and matching head wrap - were typical of that region.
But as she walked through the night, she pulled a cloth over her head and kept her face down. There are no other women out on the street after dark in this part of town, only men, either singularly or in pairs, striding through the cold desert night to their unknown destinations.
"If it was not so cold, then I would have more clients. But people don't like to turn out in the cold so at the moment, I get about five a night," said Janine as she headed back to the brothel to make sure she got her share of the night's business.
Winter daytime temperatures can reach 30 degrees centigrade or more in the desert capital, but when the sun sets they drop to a chilly 10 degrees or less.
Some minutes pass and there is a knock at the door and in walks Femi, a Nigerian woman of 38 years but who looks much older. She is a sex worker at the same brothel as Janine.
Like her colleague, she says the police are her biggest problem: "When they catch us at the brothel, they demand money - there is no fixed price. They take whatever we have."
Janine and Femi are among 12 women working at the El Mina brothel. They say they service a mixed bunch. There are fair-skinned Bidan Moors, who form the ruling elite in Mauritania, and black Africans, rich and poor.
Sex is sold at a flat rate of 1,000 Ougiya [US$3], but the women only get half the money. The rest goes to their brothel owner, or pimp.
Both women say that they religiously use condoms, thanks to free but discreet distribution by an NGO working with more than 200 women in this part of Nouakchott alone.
"I have male condoms and female condoms. I use which ever the client prefers but I never have sex without one, not even for more money," said Femi.
Femi has a 13 year-old son that she is putting through school by herself, but she cannot tell him how she makes her money.
"He does not know and he must never know," she insists, shuffling nervously in her plastic seat and pulling her shabby black shawl more tightly around her head and shoulders.
"This is dirty work. I cannot tell anybody about this. Not my son, not my neighbours, I tell them I have other work," she said.
Femi lives with her son in another part of town. She won't say where. She sends her son to school, as she comes from a family that values education highly.
Femi completed two years at a higher education college in Lagos. Her father is a teacher and her mother a headmistress.
She read all about HIV/AIDS when she was at college and, like Janine, she says that she always uses a condom, even if the client offers to pay more sex without one.
The same NGO that gives out the free sheaths, also provides basic free health care. The organisation, which does not want its name publicised in a country where sex and AIDS are taboo topics of public conversation, also instructs the women how to use the condoms properly.
"They take care of me. I used to get STDs (sexually transmitted diseases) - I would fall sick and get fevers and body pains and not be able to work, but not any more," Femi said.
Over the past four years, the NGO has encouraged 42 women working in El Mina to get tested for the HI virus. Twelve of them turned out to be HIV positive and at 29 percent, that HIV prevalence rate is far higher than Mauritania's official national figure of just 0.6 percent.
Femi's parents, like her son, don't know she is a prostitute. They think she is trading plastic goods, like she used to do back home.
Before she left in Nigeria in 1991, she had a good business and managed to save over US$3,000. With the cash in her pocket, she left Nigeria determined to make it to Europe as a clandestine immigrant to start a new life.
But in the bustling port city of Nouadhibou on Mauritania's northern border with the Western Sahara, she lost all her savings to a gang of people traffickers.
"They told me they would take me to Spain - a Mauritanian man and a French man. I gave them my money and then I never saw them again," she said, her bottom lip rising into a fearsome grimace.
All of the women that work at Janine and Femi's brothel are foreigners - or at least say they are. The shame of sex work is too much for a Mauritanian woman to admit to, according to the aid workers who help them.
Mauritania is a strict Muslim society and sex outside marriage is not supposed to exist. And it is certainly not publicly acknowledged.
The sex workers lose a lot of their money to their pimps and the police, but at least at the brothel there is some sense of safety in numbers and locals know where to come to buy sex.
But for the more discerning man with deeper pockets, keen to find a fair-skinned Bidan Moor partner, another more discreet version of prostitution is on offer.
He will be introduced to an agent who will show him photos of available young ladies from a catalogue. This intermediary will then arrange an assignation at a place of mutual convenience for a fee that can range from a handful of dollars to several hundred.
Buying sex from one of these women requires either good connections or a fat wallet and usually both, explained one aid worker closely involved in HIV/AIDS awareness activity.
"Years ago there used to be something called 'a lady's friend' - which was basically a gay guy that a rich Moor would trust with guarding the fidelity of his wife in his absence," he explained.
"From this tradition it was quite easy for a brothel or pimp-controlled system to develop. These days, it's not unusual for brothel pimps to be homosexual. Or, sometimes the pimp is a man dressed as a woman," he continued.
But like poor countries all over the world, the lobbies of the smartest hotels are a rich picking ground.
"You can go to the big hotels these days and you see young women escorting the men - basically this is just lucrative prostitution. These young girls can earn hundreds of dollars a night."
"It is very difficult to get them to stop what they are doing. The best we can do is inform them of the risks," he shrugged.