Women and girls may resort to exchanging sex for food, shelter, or money to meet their daily living needs for themselves and their families in order to survive another day.
Sixteen-year-old Stacey narrowly escaped what could have been a life of poverty and prostitution on the streets of South Sudan's capital Juba when she was taken into a shelter and offered safety and schooling.
South Sudan's civil war, which erupted in late 2013, has uprooted a quarter of the population, shattered families and left thousands of orphans, abandoned children and runaways to fend for themselves in the city.
With few options, sex work has become a form of survival for many girls and young women.
While there are no accurate figures to gauge the extent of child prostitution in the scrappy, low-rise city, the steady deterioration of South Sudan's security and economy has undoubtedly exacerbated the problem, say humanitarian workers.
"Women and girls may resort to exchanging sex for food, shelter, or money to meet their daily living needs for themselves and their families in order to survive another day," said Jennifer Melton of the U.N. children's agency UNICEF.
South Sudan descended into civil war after President Salva Kiir fired his deputy, unleashing a conflict that has spawned armed factions often following ethnic lines.
The United Nations has warned of a possible genocide, millions face famine and an estimated 3.5 million have fled their homes, 2 million of them children.
In December, a U.N. independent commission said sexual violence had reached "epic proportions" in South Sudan and that 70 percent of women in Juba had suffered some form of sexual assault since the end of 2013.
"During conflict, parents are unable to protect or care for their children, they get separated and children on their own despair and do not hesitate to use the only asset they have, which is selling their body to survive," said Cathy Groenendijk of Confident Children out of Conflict (CCC), an organisation caring for vulnerable children like Stacey.
Groenendijk and her team of social workers, psychologists and nurses have been running a children's shelter in Juba for a decade: a cluster of small buildings behind a barbed wire wall and big metal gate.
Inside the tiny oasis, clothes hang to dry and energetic children play on swings, while older residents ready the younger ones for dinner. The children attend school in Juba and return to the shelter to sleep, eat and socialise.
Stacey, the daughter of an absent father and alcoholic mother moved from her hometown of Terekeka to the capital with her mother and sisters when she was about eight years old.
"Life in the village was dangerous and my mother and father were not good because he had two (more) wives," said Stacey, who did not want to give her full name.
But city life proved even more dangerous.
"It was worse, because there are many boys and men who like to do bad things to girls, we were not safe," said Stacey, who recalls fending off an intruder who broke into her home and tried to rape her sister as she slept.
RED LIGHT DISTRICT
Living in poverty with a drunken mother in an unsafe neighbourhood, Stacey could have followed other girls in her area and turned to prostitution for a steady income.
"Many in the area where I was living (did this)," she said. "Young girls - 12 or 14."
Most of her friends were either forced to marry young or moved to the squalid district of Gumbo, west of the Nile river, where women and girls sell sex to businessmen, traders and foreigners inside dingy metal shacks.
Fifteen-year-old Jenna is one of more than 200 women and girls – according to CCC – who live and work in Gumbo's warren of crowded, unpaved streets.
"They were forced into prostitution and they know no other life. Their parents died during the war," said Groenendijk.
"The conflict makes it difficult to bring stability to the girls' lives. Mothers often see (prostitution) as a last resort to provide for their children."
Jenna came to Juba in search of a better life after her parents were killed in an attack on their village. Unlike Stacey, she was unable to escape a life of "survival sex".
"When my parents died, I ended up all by myself. It took me several days to get to Juba, and once I was here, I didn't know where to go," she said.
For some time Jenna - who did not want to give her real name – slept under market stalls at night, until a group of men attacked her.
"They ripped off my skirt and assaulted me ... I can't describe what they did to me, it was humiliating and has altered my life forever," she said.
After that night, the men kept returning. "They gave me glue and said I would feel much better if I inhaled it. They also continued to rape me," said Jenna, shoeless and wearing a denim skirt.
Soon after the attack Jenna was diagnosed with HIV. "I felt as if I had been punished. I was homeless and knew that I could never afford the medication," she said.
Jenna now lives in a room in Gumbo furnished with a single metal bed and earns less than $1 per client.
"I wanted to give up many times, but I have to believe that I can leave all this behind one day. It's what keeps me going," she said.
CCC offers some healthcare to Jenna and girls like her and the chance to learn skills like basket-weaving and jewelry-making. But it is not enough to keep them from selling sex.
"Some of these young women have died or moved to other places. Few of them ... have been able to claw their way out of a life of prostitution," said CCC psychologist Lisette Suarez.
Far from the scorching alleys of Gumbo, Stacey is finishing her homework in a purpose-built classroom inside the shelter, while a gaggle of children play in the dusty courtyard. She is set to finish middle school in a few months.
She still sees her old friends - many of whom are surviving by selling sex.
"Sometimes I talk to them but they don't listen," she said. "I tell them: you can see my life and yours, there is a big difference, you are not happy and I am happy. You are not in a safe place, but I live in a safe place."