The attack late yesterday hit a car in a military camp in Al-Qaeda-controlled Mukalla, capital of the vast desert province of Hadramawt.
The official, who did not want to be named, said a local Al-Qaeda chief was among those killed.
A second Al-Qaeda vehicle was targeted yesterday evening in a drone strike in the town of Ghil Bawazir in the same province but there was no word of casualties, he said.
Washington has repeatedly targeted militants from Al-Qaeda in the Arabian Peninsula in drone strikes in Yemen.
The jihadists have exploited months of fighting between loyalists of Yemen's exiled government and Iran-backed Huthi rebels to consolidate their grip on Hadramawt and its capital Mukalla - a city of more than 200,000.
Meanwhile, in the battleground southern city of Aden, four civilians were killed and scores wounded today by mortar fire blamed on the Huthis, according to a medical source.