(CNN) -- Terrorist groups such as Boko Haram prey on girls because they fear them, Malala Yousafzai told CNN's Christiane Amanpour on Wednesday, adding her voice to the outcry over the mass kidnappings of Nigerian girls.
Malala, the Pakistani girl who made a miraculous recovery after being shot in the head by the Taliban, said women are targeted by those who fear a society in which women are empowered.
Boko Haram has kidnapped hundreds of Nigerian schoolgirls, an act that has become the focal point of a worldwide social media campaign demanding their return.
The Malala Fund is launching a Nigerian girls education campaign around the issue. The 16-year-old human rights advocate first spoke up about the kidnappings last week.
"When I heard about girls in Nigeria being abducted, I felt very sad, and I thought, 'my sisters are imprisoned now,'" Malala said. "The girls in Nigeria are my sisters and its my responsibility that I speak up for my sisters."
Boko Haram are extremists who don't understand Islam, she said.
The religion, she says, calls for empowerment through education, not a snuffing of it.
"They should go and they should learn Islam, and I think that they should think of these girls as their own sisters. How can one imprison their own sisters and treat them in such a bad way?" she said.
Everyone should speak up for the kidnapped girls, she said.
In a photo released on social media, Malala holds a sign reading #BringBackOurGirls, joining the chorus of social media activity repeating the same demand.
Nigerian President Goodluck Jonathan has been under fire over accusations the government initially ignored and then later downplayed the abduction of the girls.
Jonathan has also accepted an offer of U.S. military support in the search for the girls.