The incident took place when tribal police were patrolling the Alam Gudar area, some 30 kilometres southwest of Peshawar, tribal administration chief Shafeerullah Khan told AFP.
"Six khasadar (tribal policemen) were martyred after unknown gunmen fired at their patrol vehicle," Khan said, adding that three others were wounded.
A local security official confirmed the ambush and casualties.
There were no immediate claims of responsibility for the attack.
Khyber is home to Taliban insurgents and militants from extremist group Lashkar-e-Islam, led by local warlord Mangal Bagh.
Washington has branded the tribal belt a global headquarters of al Qaeda and wants Pakistan to do more to fight insurgents streaming across its border into Afghanistan.
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