Three drones were used in the operation in Raqa, the de facto IS capital in war-torn Syria, and "one of them was British," the official said on condition of anonymity, adding that US drones had fired the Hellfire missiles.
The official said Britain was "very involved" in the effort to hunt down "Jihadi John," whose real name is Mohammed Emwazi.
The British citizen, clad and black and masked, appeared in a string of graphic videos showing the beheading of Western hostages.
The three drones used in the operation were MQ-9 Reapers, the official said.
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