Trafficking of Kenyan children from impoverished villages to towns and cities for domestic labour, sex work and to beg is on the rise, experts said, with most victims being adolescent girls.
Poverty, dysfunctional families and a lack of access to secondary education force children to seek work in urban areas, where they often exploited by traffickers.
"One of the recently growing phenomena is children being trafficked domestically, or within the country, from rural areas into urban areas," Angela Nyamu, country director for the child rights organisation Terre des Hommes, said at the launch of a project to combat child trafficking.
While there are no statistics on child trafficking in Kenya, anecdotal evidence suggests increasing numbers of children from rural homes are moving to urban areas in the hope of improving their lives.
High fertility rates, coupled with rural poverty and land scarcity, drive more than 250,000 Kenyans into cities each year, according to the World Bank, which predicts that the majority of Kenyans will live in urban areas by 2033.
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A third of Kenyans, or around 12 million people, live in urban centres, according to the 2009 census, up from five million, or 19 percent in 1999.
Kenya's 40 million population is growing by one million every year, according to the World Bank, and is likely to double by 2045.
In Nairobi's sprawling slums, which house two-thirds of the city's three million people, trafficked children work in brothels, bars and the drug trade, Terre des Hommes research found.
"Girls as young as nine years old reportedly work in brothels and as pole dancers in clubs," it said, adding that some are "lured with just a packet of chips".
Children are also used as beggars, scrap metal collectors and petty criminals.
"There are actually cartels and gangs involved," Nyamu said. "People are making money out of it."
Kenya is a source, destination and transit country for trafficking. It has been in the U.S. Department of State's Tier 2 watch list for three years, indicating that it is not doing enough to combat trafficking.
There is often a fine line between economic migration, where people move for better living standards, and child trafficking, which the United Nations defines as the recruitment, transfer and receipt of children for the purpose of exploitation.
Parents living in poverty in rural Kenya traditionally send their children to live with relatives in urban areas, but they often end up being exploited.
"Child trafficking is often perceived as being a normal and accepted practice," Terre des Hommes research found. "Parents in the rural areas believe their children are in very good hands."
One girl, orphaned at the age of six, was tricked into doing unpaid domestic work from the age of 12.
"A relative picked me up from home promising to sponsor me to a hairdressing course," she said. "I ended up being her house-help. I stayed with her for five months without a salary."
She worked unpaid for several women. One employer's husband tried to rape her. Another employer used her to traffic marijuana and sell illegal brewed alcohol.
"I had no choice," she said. "You can't live without eating ... I was too desperate to run away."
Experts said it is important to provide greater support to families where children are hungry and abused.
"When families break up, when we have unstable families, gender-based violence in the families, what happens? In most cases, children are running away from those families," said Jane Muyanga, Nairobi's coordinator of children's services.
Children are most at risk after completing primary school, around age 12, as half do not continue to secondary school.
Either their families cannot afford the fees of around 25,000 Kenya shillings ($280) a year, or their exam results were too poor to win them a place in secondary school. Children who are not in school are expected to fend for themselves.
"Many of these children are then the ones who end up in domestic work and also in commercial sexual exploitation," said Wambui Njuguna, regional director of programmes for the African Network for the Prevention and Protection Against Child Abuse and Neglect.