Source: Thomson Reuters Foundation
"I want to go to Italy because I want to make money. If it is prostitution, I'll do it."
Sitting on the floor surrounded by vials, animal bones and sheets stained crimson with blood, spiritual doctor Olor Elemian described how he scares girls into blind obedience with potions and spells known as "juju".
Pimps, madams, smugglers and even parents bring girls to his shrine in Amedokhian village near the southern Nigerian city of Uromi, where they drink concoctions brewed with pieces of their own fingernails, pubic hair, underwear or drops of blood.
"I can make sure she never sleeps well or has peace of mind until she pays what she owes," said the 39-year-old spiritual priest known in his neighbourhood as "Doctor".
"Something in her head will keep telling her: 'Go and pay!'"
Juju is a potent ingredient in a cocktail of coercion that keeps thousands of Nigerian women and girls in sex slavery in Europe, mostly in Italy, after making the treacherous journey across North Africa and the Mediterranean in search of better lives.
Combined with crippling debt and threats of violence, it helps perpetuate a cycle of exploitation in which many victims then become perpetrators, returning to Nigeria as "madams" to recruit more girls, police and rights groups say.
In Edo state - a southern Nigerian hub for human trafficking - many girls begin their journey into prostitution willingly. Most have little clue of the nightmare to follow.
Some even visit native doctors like Elemian of their own accord, hoping juju will help them prosper while selling sex in Italy.
"It's not how hard a person works that determines how much money she will make," he said, showing off his new mobile phone and modern bungalow, which stands out amid his neighbours' mud huts.
These trappings of wealth are all funded by grateful clients from Italy, he said.
MANAGED BY MADAMS
According to the U.N. Office on Drugs and Crime (UNDOC), more than nine in 10 Nigerian women smuggled to Europe come from Edo, a predominantly Christian state with a population of 3 million.
Traffickers in Nigeria are exploiting Europe's migration crisis, moving girls to lawless Libya, before crossing the Mediterranean to Italy, anti-slavery activists say.
"Edo women started going to Italy to buy gold and beads in the early 1980s and saw a thriving market in prostitution," said Kokunre Eghafona, a professor of sociology and anthropology at the University of Benin and a consultant researcher for the International Organization for Migration (IOM).
"They came back and started taking family and friends."
These women, known as "madams" - who make up around half of Nigeria's traffickers, UNDOC says - are mostly former victims-turned-brokers who prey on others to escape prostitution.
Many such traffickers believe they are being helpful rather than doing harm, calling themselves sponsors rather than madams, a more positive title, according to Eghafona.
Speaking from her home in the city of Warri with her one-year-old son crying in the background, madam "Mama Anna" said that with so many girls looking for traffickers to take them to Italy, she no longer needed to deceive or trick them into going.
"Some ask me what they will do when they get there," said Mama Anna, boasting of her reputation as a broker who sends interested girls to Italy to work for her older sister, also a madam.
"I tell them they will go and hustle," she said. "They ask: 'What kind of hustle?' I tell them. Some refuse to go, others agree."
BONDED BY DEBT
For an insight into what drives young women to travel to Italy and sell sex, look no further than Uromi, with its pothole-ridden roads and derelict buildings with wells in front yards - evidence of the town's lack of running water.
One neighbourhood stands out. Its nickname is "Little London" and it is known for sleek, modern houses behind imposing iron gates, many said to be funded from the proceeds of prostitution.
Faith, a 23-year-old hairdresser, travelled more than 300 km (almost 200 miles) to Uromi from her home in Akwa Ibom, dreaming of joining the ranks of thousands of sex workers smuggled to Europe each year.
"I want to go to Italy because I want to make money," she said. "If it is prostitution, I'll do it."
In the past, girls like Faith would have been tricked into prostitution, promised jobs like hairdressing or supermarket before being forced to work for pimps.
"Before, nobody knew - it was a secret thing," said 30-year-old Anita, who was sex trafficked to Italy in 2011, after being deceived into thinking she was going to work as a hairdresser.
"But now, even children know that when you get there, it is prostitution."
After escaping her traffickers, Anita spent days on the streets. She was finally arrested and deported back to Nigeria.
Before arranging their passage through contacts in Libya, traffickers like "Mama Anna" make the girls sign a contract to finance their move - leaving them with debts that can spiral to tens of thousands of dollars and take years to pay off.
Girls are then taken to a spiritual priest, who conducts the "juju" rituals designed to bind them to their traffickers.
Such rites instil fear in victims, who believe that they or their relatives may fall ill or die if they disobey their traffickers, go to the police or fail to pay off their debts.
Fearful that the juju "spell" may be turned on them, many Nigerian parents become complicit, insisting that their daughters obey their traffickers, testimony from Italian court documents shows.
It's then on to Europe via well-trod smuggling routes through Niger and Libya.
"PUBLIC ENEMIES"
At Uromi market, several stalls display secondhand winter jackets and mittens, which one trader, Linus, described as a thriving market due to the number of people heading to Europe.
More than 12,000 Nigerian women and girls have reached Italy by sea over the past two years - a six-fold increase over the previous two-year period - with around four in five of them trafficked into sex work, according to data from the IOM.
Human trafficking by Nigerian organised crime gangs is one of the greatest challenges facing police forces across Europe, according to the EU's law enforcement agency, Europol.
For Nigeria's anti-trafficking agency, NAPTIP, efforts to combat the traffickers are being thwarted not only by the criminals themselves, but also by members of the public.
"Everybody believes that the streets of Europe are paved with gold," said Arinze Orakwe, an official at NAPTIP. "People see us as a problem, as stopping them from reaching El Dorado.
"One mother asked me if I would prefer her daughter to have sex with a young boy in Edo and get pregnant, when she can do the same thing in Europe and earn foreign currency," he said.
NAPTIP officials have been attacked by mobs in Edo while informing people of the dangers of trafficking, and angry relatives often snatch their daughters away from training or rehabilitation centres and threaten the staff, Orakwe added.
"These people, they are enemies, because this country is too rough now," said Igose, a mother-of-eight who relies on money sent by her 22-year-old daughter in Italy to feed her family.
While Igose in Benin City, the capital of Edo state, fears for the future of her family, in neighbouring Uromi, Faith is still searching for a madam to arrange her passage to Italy.
Sometimes she is tempted to abandon her dream.
"I see pictures on my phone of people drowning in the sea," she said. "It is risky".
By Adaobi Tricia Nwaubani