The incident occurred on Friday.

Police have not arrested anyone so far.

No group has claimed responsibility for burning down the 13 schools in the region.

Malala Yousafzai asked authorities to rebuild the schools and ensure that students return for studying.

"The extremists have shown what frightens them most - a girl with a book. We must rebuild these schools immediately, get the students back into their classrooms and show the world that every girl and boy has the right to learn,"Malala tweeted.

She was attacked by terrorists in 2012 for promoting girl's education.

Pakistan's Prime Minister-elect Imran Khan also condemned the act and tweeted: "Shocking & condemnable torching of schools in GB, more than half of them girls' schools.This is unacceptable & we will ensure security for schools as we are committed to focusing on education, esp girls' education which is integral to Naya Pakistan."