Attacks on Shiites began Friday as Shiites observe the festival of Ashura marking the death of Prophet Muhammad's grandson, Imam Hussein.
In Hangu, shooting broke out after the mortar shell exploded and at least two people were killed and 14 others, mostly policemen, were injured, a BBC correspondent said.
Pakistani President Pervez Musharraf deployed army and paramilitary troops to the town and local officials imposed a curfew.
In the nearby town of Bannu, another rocket attack on a Shiite mosque injured 11 worshippers, the report said.
Monday, a Taliban-trained 17-year-old suicide bomber killed himself and two others at a police checkpoint in the northwestern town of Dera Ismail Khan. Seven others were injured, the Pakistan Tribune reported.