Authorities say the bodies were found Sunday in the western province of Herat
No one has claimed responsibility for the killings.
Security is a top concern ahead of the election. Afghan election officials have said that more than 900 polling stations will not open because voter safety cannot be ensured.
In eastern Afghanistan, NATO says Afghan and international coalition forces have killed a Taliban commander and seven other insurgents.
The international alliance says the militant commander killed Saturday in the operation in the Paktiya province was responsible for coordinating the movement of explosives and fighters.
Elsewhere on Saturday, NATO says coalition forces stopped attacks by insurgents, some of them wearing American military uniforms and suicide vests, at two U.S.-run bases in eastern Afghanistan.
A NATO spokesman says the insurgents opened fire with machine guns and rockets on Forward Operating Base Salerno and nearby Camp Chapman in Khost province.
The coalition says its forces killed 15 insurgents near Salerno, six near Chapman and three others in an air strike as they tried to escape the area. Five insurgents were detained.
On Sunday, NATO said Afghan and coalition forces had captured a Haqqani Network commander and two militants who had been involved in the attacks on the two U.S.-run bases.
NATO said two members of the international security force were killed Saturday in an insurgent attack in eastern Afghanistan, but it did not give specifics.
NATO says on Sunday in southern Afghanistan, two ISAF servicemembers died in separate insurgent attacks.
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