Around 120 million girls - one in 10 - worldwide have been forced into sex before they are 20, according to a United Nations report.
The report from the UN children's agency Unicef found these children were routinely exposed to physical, sexual and emotional violence ranging from murder and forced sexual acts to bullying.
It also revealed 95,000 youngsters under 20 were murdered in 2012 alone.
Nigeria, where the Boko Haram terrorist group abducted more than 200 schoolgirls in April and threatened to marry them off, had the largest number of child victims, with almost 13,000 deaths in 2012, followed by Brazil with about 11,000.
In the West, America had the highest child homicide rate.
Unicef executive director Anthony Lake said violence "cuts across boundaries of age, geography, religion, ethnicity and income brackets."
He added: "It occurs in places where children should be safe, their homes, schools and communities.
"Increasingly, it happens over the Internet, and it's perpetrated by family members and teachers, neighbours and strangers and other children."