UNITED NATIONS (AP) — The U.N. women’s agency has kicked off 16 days of activism against gender-based violence, targeting the often-unpunished crime of rape that afflicts women and girls in every country and has been used as a weapon in conflicts from Bosnia and Rwanda to Syria and Myanmar.

Around the world Monday, tens of thousands of women marched on the International Day to End Violence Against Women to support the campaign, “Generation Equality Stands Against Rape!”

Exact numbers are notoriously difficult to determine due to many victims’ fears of reporting rape or sexual assault.

But UN Women says approximately 15 million girls worldwide ages 15 to 19 have experienced forced sexual intercourse or other sexual actions. One of every three women worldwide is estimated to have suffered either physical or sexual violence.