A U.S. airstrike killed more than 150 people in an attack aimed at the terrorist group al-Shabab in Somalia, according to Navy Capt. Jeff Davis, a Pentagon spokesman.

The drone strike hit the Raso training camp approximately 120 miles north of Mogadishu. According to a senior defense official who spoke on the condition of anonymity to speak frankly about the operation, there were no civilian casualties in the strike, though the Pentagon is still assessing the situation on the ground. It is not clear how many aircraft were involved.

According to the official, U.S. intelligence assets had been watching the camp for several weeks prior to the strike. The camp was home to a large group of fighters who were scheduled to depart in the coming days. The official said the strike was authorized because there was an “imminent threat” to U.S. and African Union forces in the region.

There is a small detachment of U.S. advisers in Somalia aiding the African Union troops stationed in the war-torn country. The drones that carried out the strike are more than likely to have been flown from the small U.S. drone base at Chabelley Airfield in nearby Djibouti.

(c) 2016, The Washington Post · Thomas Gibbons-Neff