Along with the fatalities, at least five other people were injured in the explosion, which occurred at about 8 a.m. local time (03:30 GMT), Afghan police said adding the attack was aimed at a U.S. military SUV carrying coalition soldiers.
A Taliban member phoned reporters to claim responsibility for the attack.
NATO officials said the soldiers were not hurt, but witnesses said two foreign soldiers were wounded, and that one of them was carried from the damaged vehicle to another car. The attacker died.
Clashes with Taliban fighters in Afghanistan's western province of Farah in an ongoing operation have killed at least 45 militants, and left three Afghan troops dead and another four wounded, an Interior Ministry official said on Thursday.
He said the joint operation involving Afghan troops and police, and the U.S.-led international coalition began on Wednesday and continued in the Bala Baluk district of Farah on Thursday. Losses among coalition troops have not been reported.
