The CIA and the Joint Special Operations Command (JSOC) had launched a secret drone campaign targeting the prominent operatives of ISIS in Syria, the Washington Post reported on Tuesday.
Although the CIA's Counterterrorism Center (CTC) has been given an expanded role in identifying and locating senior ISIS figures, US officials said the strikes are carried out exclusively by JSOC.
"These people are being identified and targeted through separate effort," said a senior US official familiar with the operation, referring to the British militant, Junaid Hussain, and others killed in recent weeks.
Hussain, a 21-year-old hacker, who was killed in Syria on June 22, is believed to be the architect of the terrorist group's effort to use social media to incite attacks in the United States.
The US conducted about 2,500 air strikes against ISIS since last September in Syria and Iraq, but they were unable to push back the group significantly.
Turkey and the US signed an agreement on Aug. 27, and US military began to use the Incirlik Air Base in southern Turkey to launch air raids against ISIS militants.
Two days after the agreement, Turkey and US-led coalition forces conducted their first joint operation and hit ISIS targets in Syria.