An estimated 21 million people worldwide are trapped in conditions of contemporary slavery, including some five million children, a UN office said.
"Slavery is not something that belongs to the past but a cruel reality of our age," the UN High Commissioner for Human Rights said on Monday in a media statement.
They also announced an upcoming event which will showcase the extent of modern-day slavery, Xinhua news agency reported.
The event, entitled "Revealing the Child Faces of Modern Slavery", will be organised by the UN Human Rights Office to mark International Day for the Abolition of Slavery on December 2.
The event is also to mark the 25th anniversary of the UN Voluntary Fund on Contemporary Forms of Slavery, which since it's establishment in 1991 has supported of thousands of men, women and child victims of various forms of slavery.
In 2016, the Fund issued grants to projects in 34 countries, helping more than 29,000 victims, a third of whom were children, the UN rights office said.