The official, who did not want to be named, said the vehicle was struck in the al-Qatn district of the vast Hadramout province in eastern Yemen.
Residents said the car was struck by one of three missiles fired from a plane and that charred bodies were pulled from it afterwards.
It was not clear if there were other casualties in the attack. Washington, which fears the spread of militancy in Yemen, has stepped up attacks by unmanned drones this year.
Al Qaeda in the Arabian Peninsula is based in Yemen and has mounted operations in neighbouring Saudi Arabia and against the United States.
Two men described by the Yemen government as militants were killed in a US drone attack on a car in central Yemen on Tuesday.
The impoverished Arabian Peninsula state has been in turmoil since an uprising erupted last year and forced veteran ruler Ali Abdullah Saleh to step down in February.
Militants gained ground during the unrest, taking control of several towns in south Yemen.
The army, with backing from the United States, has forced them out of some areas this year but they have hit back with a series of suicide bombings targeting government institutions.
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