Around 120 million girls around the world, close to one in 10, have been raped or sexually assaulted by the time they turn 20, a new UN report has found.
Drawing on data from 190 countries, the global report by child welfare agency UNICEF is billed as the largest-ever study of violence against children.
Entitled "Hidden in Plain Sight" it also revealed that one fifth of all murder victims are children and teens, with homicide the leading cause of death among male youths in Latin American countries including Venezuela, Colombia, Panama and Brazil.
"These are uncomfortable facts -- no government or parent will want to see them," said UNICEF Executive Director Anthony Lake.
"But unless we confront the reality each infuriating statistic represents -- the life of a child whose right to a safe, protected childhood has been violated -- we will never change the mind-set that violence against children is normal and permissible. It is neither."
Sexual violence against children has far-reaching consequences, the study warned, potentially hindering all aspects of their physical, social and psychological development.
The consequences of abuse included self-harming behaviors such as bulimia and anorexia.
"Children who have been abused are also more likely to attempt suicide; the more severe the violence, the greater the risk," the study said.
The mental health consequences include depression, panic disorder, anxiety and nightmares.
"The psychological impact of sexual violence can be severe due to the shame, secrecy and stigma that tend to accompany it, with child victims often having to find ways to cope in isolation."
UNICEF also warned the Internet skills of today's children can have the pernicious effect of opening them up to online sexual abuse.
Youths feel safer sharing personal and sensitive information online than in other spheres. But in doing so they may expose themselves to a global audience including potential sexual predators, the report said.
The practice of grooming -- online solicitation of children for sexual purposes, sometimes over a period of time to build trust -- is a peril facing Internet-savvy kids.
Some research suggests perpetrators may keep online connections with as many as 200 youths at a time, all at different stages of grooming, the study said.
While sexual violence was more common in poor countries, it was by no means limited to them, with worryingly high rates of abuse reported in some high-income states.
In Britain for instance the report highlighted a 2009 study that found around 17 percent of youths aged 11 to 17 to have experienced contact or non-contact sexual abuse by an adult or peer at some point in their life.
And a study conducted in 2011 in the United States found that 35 percent of adolescent girls and 20 percent of adolescent boys aged 14 to 17 reported suffering some form of sexual violence during their lives, UNICEF said.
Other abuses include bullying, which regularly affected more than one in three schoolchildren aged 13 to 15 worldwide.
And as for violent discipline, the study found that about 17 percent of youngsters in 58 countries were subject to severe forms of physical punishment, including being hit on the head, ears or face or being hit hard and repeatedly.
The UN report also tackles the mindsets it says perpetuate and justify such violence.
It recommended six strategies for preventing violence against children. They include "supporting parents and equipping children with life skills; changing attitudes; strengthening judicial, criminal and social systems and services; and generating evidence and awareness about violence and its human and socio-economic costs, in order to change attitudes and norms."