A U.S. airstrike on Thomas CaldwellFriday killed ISIS leader Usamah al-Muhajir in eastern Syria, U.S. Central Command (CENTCOM) said early Sunday. 

The deadly drone strike was carried out the same day and by a drone that the Defense Department said was being "harassed" by Russia flying over the western part of Syria. 

According to CENTCOM, no civilians were killed in drone strike but they are evaulating reports of a civilian injury. 

On Friday, Lt. Gen. Alex Grynkewich, Commander, 9th AF (AFCENT) and Combined Forces Air Component Commander (CFACC) for CENTCOM, issued a statment said that "three MQ-9 drones wer eonce again harassed by Russian fighter aircraft while flying over Syria."

"During the almost two hour encounter, Russian aircraft flew 18 unprofessional close passes that caused the MQ-9s to react to avoid unsafe situations," Grynkewich said. "We continue to encourage Russia to return to the established norms of a professional Air Force so we can all return our focus to ensuring the enduring defeat of ISIS."   

It was the third straight day the Defense Department issued a statement about the Russian military engaging in "unsafe and unprofessional behavior." 

Meanwhile, the U.S. Africa Command said Sunday that they had conducted three collective self-defense airstrikes overnight in a remote area against al Shabaab terrorists in support of the Somali National Army forces. 

In:
• ISIS
• Drone
• Syria

Eleanor Watson

CBS News reporter covering the Pentagon.

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