NEW : Teen killed when Four bombs explode outside music festival . three killed after suspected U.S. missile strike fired from drone , official says . Attack believed to be fourth in U.S. since early November . Hangu bombing leaves at least three people dead in northwest .
NEW : Teen killed when three bombs explode outside music festival . Four killed after suspected U.S. missile strike fired from drone , official says . Attack believed to be fourth in Pakistan since early November . Mosque bombing leaves at least three people dead in northwest .