The drone yesterday targeted a car driving in Habban, killing "two Al-Qaeda fighters and wounding their driver," one of the sources said.
The strike comes after an American drone attack on Saturday killed two other presumed Al-Qaeda members in their vehicle in Marib province, east of the capital Sanaa.
Washington, which views Al-Qaeda's Yemen-based branch as its most dangerous, acknowledged on May 7 that a "very small number" of US military personnel have also been deployed in support of the operation to retake former Al-Qaeda stronghold of Mukalla.
The United States regularly conducts air strikes against Al-Qaeda. A March strike on a training camp west of Mukalla killed more than 70 fighters.