WASHINGTON — For the third time in a week, the United States military carried out an airstrike on Thursday against Islamic State fighters in southern Libya amid indications the terrorist group was seeking to exploit the country’s civil strife to increase its recruiting.

The Pentagon’s Africa Command said in a statement on Friday that the strike — which other officials said was carried out by an Air Force Reaper drone based in neighboring Niger — killed 17 militants in an unidentified location in southwest Libya.

“We will continue to pursue ISIS-Libya and other terrorists in the region, denying them safe haven to coordinate and plan operations in Libya,” Rear Adm. Heidi Berg, the command’s director of intelligence, said in the statement, noting that the strike was coordinated with the Libyan government in Tripoli.

The strike was the latest in a flurry of attacks in a largely ungoverned portion of the country. Earlier, the Africa Command said that on Sept. 19, an airstrike killed eight ISIS fighters in a compound in Murzuq, Libya, nearly 600 miles south of Tripoli, the capital. Five days later, the military said it killed 11 more fighters in an airstrike in the same area.