Two missiles fired by unknown militants landed at Kalaya Chowk, headquarters of lower Orakzai agency, killing a personnel of Balochistan Levies force and a civilian on the spot, and critically injuring three others including a minor.
The injured were rushed to a nearby hospital in Kalaya where they are battling for their lives.
Last Friday, six soldiers were killed when extremists opened fire on check posts in the same agency.
Hangu district bordering Orakzai agency has been declared the most sensitive district for Muharram by the provincial administration.
Army has said that more than 1,100 terrorists were killed in Zarb-i-Azb operation launched against Taliban in North Waziristan in mid-June while around 50 were killed in Khyber-I offensive against militants in the Khyber tribal district.