SANAA, Yemen -- The U.S. military conducted an airstrike Tuesday against an al Qaeda training camp in Yemen, causing dozens of casualties, a Pentagon spokesman said.

Pentagon spokesman Peter Cook said the training camp was located in the mountains, and was being used by more than 70 terrorists belonging to al Qaeda in the Arabian Peninsula (AQAP).

Cook did not specify the location of the camp. But Yemeni security officials and a witness said the airstrike hit a former military base that had been taken over by al Qaeda militants about 47 miles west of the terror group's stronghold city of Mukalla.

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"We continue to assess the results of the operation, but our initial assessment is that dozens of AQAP fighters have been removed from the battlefield," Cook said.

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

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

"This strike deals a blow to AQAP's ability to use Yemen as a base for attacks that threaten U.S. persons, and it demonstrates our commitment to defeating al-Qaida and denying it safe haven," Cook said.

Yemen has been left fragmented by war pitting Shiite Houthi rebels and military units loyal to a former president against a U.S.-backed, Saudi-led coalition supporting the internationally recognized government.

The war has given AQAP a freehand to expand and seize cities and large swaths of land. Militants from the Islamic State of Iraq and Syria (ISIS) have also taken advantage of the chaos to wage a series of deadly attacks across the country.