The U.S. Central Command said on Sunday it conducted a drone strike on July 7 that killed an ISIS leader in Eastern Syria.
It used the same MQ-9 drones in the attack that had "earlier in the day been harassed by Russian aircraft in an encounter that had lasted almost two hours", it said in a statement.
"U.S. Central Command conducted a strike in Syria that resulted in the death of Usamah al-Muhajir, an ISIS leader in eastern Syria," it said without giving any more details on al-Muhajir.
Washington has in the last year stepped up raids and operations against suspected ISIS operatives in Syria, killing and arresting various of its leaders who had taken shelter in areas under Turkey-backed rebel control after the group lost its last territory in Syria in 2019.
The U.S.-led campaign which killed former ISIS head Abu Bakr al Baghdadi, who had declared himself the "caliph of all Muslims", has since targeted its surviving leaders, many of whom are thought to have planned attacks abroad.
U.S. military commanders say ISIS remains a significant threat within the region, however, though its capabilities have been degraded and its ability to re-establish its network weakened.
Islamic State controlled one-third of Iraq and Syria at its peak in 2014. Though it was beaten back in both countries, its militants continue to wage insurgent attacks.
(Reporting by Adam Makary and Omar Abdel Razek and Suleiman al Khalidi; Editing by Elaine Hardcastle and Hugh Lawson)