Sexual exploitation of children in Kenya has reached very high levels, the United Nations Children's Fund (UNICEF) stated in a report launched on Tuesday in the Kenyan capital, Nairobi.

A study by UNICEF and the Kenyan government found that at least 15,000 girls in four districts on the Kenyan coast – Mombasa, Kilifi, Malindi and Kwale - were engaged in casual sex-for-cash.

"These girls, aged 12 to 18 years, make up 30 percent of the total population of girls from these districts in this age range," UNICEF said. "A further two to three thousand girls and boys are involved in full-time sex-for cash. Some of them are paid to perform the most horrific and abnormal acts."

According to UNICEF, at least 45 percent of the girls in the survey began selling sex for cash, goods or favours at only 12 or 13. More than 10 percent of girls involved in prostitution began transactional sex when they were younger than 12.

According to the report, while many children are driven into transactional sex because of poverty, the high level of acceptance of child sex work in a significant group linked with tourism and beach commerce makes it relatively easy for children to drift into casual sex in exchange for no more than extra pocket money.

Kenyan Vice President Moody Awori, who launched the report, said sexual exploitation of children in the country was a "shocking reality" and "a vice that continues to grow to horrific magnitude particularly around the coastal region".

The study shows that Kenyan men are the worst culprits in sexual exploitation of children, making up 38 percent of the clients.

"Among tourists, Italians, Germans and Swiss ranked as the most common clients of child sex workers at 18 percent, 14 percent and 12 percent respectively," UNICEF said. "Ugandans and Tanzanians rank fifth and sixth in the client group, while British and Saudi Arabian men ranked seventh and eighth – but representatives of virtually every nationality visiting Kenya are named in the report."

Awori said the government was taking steps to promote responsible tourism: "To combat exploitation of Kenyan children by tourists, the government now requires all foreigners to state their residential address in Kenya before being allowed into the country – which helps us to monitor foreigners' activities. We will also work with other governments to urge their cooperation in promoting responsible tourism."

UNICEF’s Kenya representative, Heimo Laakkonen, said: "Tourists and Kenyans who abuse children must be arrested, brought to trial and punished. Children who are exploited for sex are the victims, they are being abused."

Laakkonen said there was a need to scale-up programmes promoting responsible tourism and expand endorsement of the Code of Conduct, which binds hoteliers and their staff to report the abuse and suspected abuse of children on their premises.

"Tourists must be made aware, right from their points of origin, that Kenya is a no-go zone for sexual exploiters of children," he said.

He said the findings of the study was part of a wider campaign by the government, UNICEF, civil society, religious organisations and the private sector in Kenya to stop violence against children.

Sexual exploitation of children is a criminal offence under Kenya’s Penal Code, but the study showed an extremely high level of acceptance of commercial sex involving children.

The sexual exploitation of children is not limited to coastal areas or to tourists, but is found across Kenya. About one in 10 children involved in sex work is initiated before they reach puberty, the report states.

"It reflects a failure of the authorities to provide protection to children and to prosecute those responsible for promoting and profiting from child sex work," the report added.

The report recommends that the government, civil society, the tourist industry, and broader private sector urgently come together to prevent and end the sexual exploitation of children.