Twelve people including children were killed in two separate militant attacks in Pakistan's northwestern Khyber district .  A Pakistani official said at least six people including two children and a woman were killed when a mortar fired by militants fell in Tirah Valley  in Khyber, expressing his conviction that the militant apparently targeted a security check post but missed it.  In another incident a group of 20 militants belonging to Askar Al Islam attacked a border guard check post.  A security said six militants were killed and 10 were injured in the ensuing exchange of fire, adding that all the wounded militants were arrested.