Child prostitution has been defined by the UN as "the act of engaging or offering the services of a child to perform sexual acts for money or other consideration with that person or any other person".
By 1990, international awareness of the commercial sexual exploitation and the sale of children had grown to such a level that the United Nations Commission on Human Rights decided to appoint a Special Rapporteur on the sale of children, child prostitution and child pornography.
Here is a list of the five countries with the highest rates of child prostitution.
The number of crimes against children in Sri Lanka increased by 64% in 2012 , compared to the previous year, a Unicef report said.
"According to Unicef and ILO [International Labour Organisation] there are 40,000 child prostitutes in Sri Lanka and 6.4% of the country's child population gets pregnant," said United National Party MP Rosy Senanayake.
Although girls are sexually exploited both in the sex industry and by sex tourists, many NGOs believe that it is boys who face greater abuse by foreign sex offenders, NGO Ecpact (Ending Child Prostitution, Pornography and Trafficking) said.
In Sri Lanka, the plantation sector has been identified as a notorious area for trafficking of children into the worst forms of child labour, particularly child domestic work and commercial sexual exploitation, according to ILO.
The National Child Protection Authority issued a warning in 2011 of an increase in child sexual exploitation, related to the rapid growth of tourism.
Child prostitution in Thailand involved 800,000 children under the age of sixteen in 2004.
According to Ecpat, due to the hidden nature of child sexual abuse reliable figures are hard to compile and cases difficult to document. Available figures estimate that currently some 30,000 to 40,000 children, not including foreign children, are exploited as prostitutes.
Sexual exploitation of children in Thailand, as in many other countries, is tremendously influenced by tourism.
"In Pattaya [ Thailand], if there were fewer foreign people coming in to buy sex, then the problem would be easier to manage," Palissorn Noja, who runs Pattaya's Anti-Human Trafficking and Child Abuse Centre, told the Huffington Post.
"They [pedophiles] have an entire worldwide network of people looking for children through human trafficking. And sex tourism makes it harder to stop."
The photographic documentary, "Underage" by photographer Ohm Phanphiroj shows the life of thousands of underage male prostitutes in Thailand.
"The film aims at exposing the rotten problem about sexual exploitation against minors and mistreatment towards children," the photographer said in a statement.
Sex trafficking is an appalling truth to many young people in Brazil, where there are half-a-million child sex workers, according to the National Forum for the Prevention of Child Labour.
Children as young as 12 are selling themselves for sex for as little as 80p in Brazil, according to an investigation by Sky News.
The shocking revelation comes as international footballers join a campaign warning fans travelling to Brazil for the World Cup to exploit children.
According to the documentary "Brazil- Children for sale", hundreds of children who live in the slums leave their homes in search of tourists, who are "eager for easy and cheap bodies", to earn money and escape poverty.
Unemployment and poverty is extremely high in Brazil and children are sometimes encouraged by their parents to start prostituting.
According to Crimes Against Children research Centre (CCRC), the numbers of juvenile prostitutes within the United States range from 1,400 to 2.4 million, although most fall between 300,000 and 600,000.
16 children as young as 13 were rescued from the sex trade in a law enforcement operation that targeted suspected pimps who brought the victims to New Jersey for Super Bowl weekend, in February 2014.
"Prostituted children remain the orphans of America's justice system. They are either ignored or, when they do come in contact with law enforcement, harassed, arrested, and incarcerated while the adults who exploit them - the pimp and their customers - largely escape punishment," said Julian Sher, author of the book Somebody's Daughter: The Hidden Story of America's Prostituted Children and the Battle to Save Them.
Inuit babies and children are being sold by their families and are "prostituted out by a parent, family member or domestic partner", according to a recent report by Canadian Department of Justice.
The sexual exploitation of children is a deeply–rooted reality in too many Canadian homes, families and communities, according to a 2011 report by a Standing Senate Committee on Human Rights.
The committee, which started the investigation in 2009, heard that in one year there were almost 9,000 reported sexual assaults against children
(many of whom belong to aboriginal communities) in Canada. The overwhelming majority of sexual abuse goes unreported.
Social service organisations have estimated the number of trafficked Canadians to be as high as 16,000 a year, but the number of children trafficked within Canada from place to place remains uncertain due to the clandestine nature of the activity, Unicef Canada said in a statement in 2009.