Around one billion children - half of all those in the world - are affected by physical, sexual or psychological violence, which has been "made worse" by lockdown measures during the pandemic, according to the United Nations.
In the first study of its kind, the report by the World Health Organization also found that approximately 40,000 children were victims of homicide in 2017.
It said the coronavirus pandemic had caused an increase in violence, as stay-at-home policies had cuts sources of support and eroded victims' ability to cope with pressures. WHO chief Tedros Adhanom Ghebreyesus called it a "disturbing" effect of Covid-19.
Around 80% of countries also lacked funding and measurable targets for prevention programmes, exacerbating the trend further, along with an increase in harmful online behaviour like cyber-bullying.