More than 370 million girls and women alive today — or 1 in 8 worldwide — have experienced rape or sexual assault before the age of 18, the United Nations children's agency said on Wednesday.

The number rises to 650 million, or 1 in 5, when taking into account "non-contact" forms of sexual violence, such as online or verbal abuse, UNICEF reported, in what it called the first global survey of the problem.

The report said that while girls and women were worst affected, 240 to 310 million boys and men, or around 1 in 11, have experienced rape or sexual assault during childhood.