A US drone strike killed three suspected members of the al Qaeda-linked group near their battlefront with arch-rivals from the Shi'ite Muslim Houthi group, tribal sources said.
The sources said the drone was used in the al-Manasseh area against Ansar al-Sharia, the local wing of Al Qaeda in the Arab Peninsula (AQAP).
The drone was still circling the area, they said.
This was believed to be the first US air strike against the militant group in Yemen since the Houthis engaged al Qaeda-linked militants in central Yemen after they captured the capital Sanaa last month.
Washington has acknowledged using drones in Yemen.
AQAP is believed to be among the most active wings of the network founded by Osama bin Laden.
In the last known drone strike in Yemen in August, three suspected al Qaeda militants were killed in the country's eastern Hadramout province.
In April, a series of drone strikes killed about 65 militants in southern and central provinces. The Yemeni army followed up with an air and ground offensive to dislodge AQAP fighters from their main strongholds in the south.
The Houthis, who hail from the Zaydi branch of Shi'ite Islam, captured the capital Sanaa in September.