Yemeni security officials and a witness say an airstrike has hit a former military base that has been taken over by al-Qaida militants near the terror group's stronghold city of Mukalla, causing casualties.

A tribal member at the site says about 40 people were killed and wounded in the Brom Maifa district on Tuesday. He didn't give a breakdown and said that bodies are still being counted. He spoke on condition of anonymity, fearing for his safety.

It's unclear who was behind the strike at the base, sometimes used as a training camp. Dozens or even hundreds of al-Qaida fighters may have been there. The base is located 75 kilometers (47 miles) west of Mukalla.

The officials spoke on condition of anonymity because they weren't authorized to talk to reporters.