A remote-controlled hobby plane, rigged with hidden explosives, killed two Kurdish Peshmerga fighters and injured two French special operations troops near Mosul, French and US sources confirmed Wednesday.
While the Pentagon has previously said the Daesh terrorist group uses simple, commercially available drones to conduct surveillance and carry small explosives, this was the first known deadly case.
According to a US defence official, the incident unfolded October 2 when a small plane with a styrofoam body was either shot down or crashed in Erbil in northern Iraq.
Two local Kurdish Peshmerga fighters grabbed the drone and took it back to their camp to inspect and photograph it, when it blew up.
"It looks like the explosive charge was hidden inside of what appeared to be a battery on some sort of a timer," the official said, speaking on condition of anonymity to discuss the matter.
A French source earlier confirmed the use of a "booby-trapped drone in Iraq," while another confirmed that two French soldiers were hurt in the incident. One of the French soldiers has life-threatening injuries.
Both commandoes have been flown back to France for treatment. The French military declined to comment.
Colonel John Dorrian, a spokesman for the US-led coalition fighting Daesh in Iraq and Syria, described the incident as a "Trojan Horse-style" attack.
"There was an improvised device on a drone. And when that was brought back to the camp, it exploded," he said.
US defence officials said the military was deploying additional anti-drone technologies to the theater, including systems that provide electronic jamming.
"We don't just let the enemy develop a capability that threatens our forces and those forces of our allies and partners and leave that threat unaddressed," Dorrian said.
France is part of the international coalition fighting Daesh, which is preparing for a major offensive to dislodge the group from Mosul, which lies 85 kilometres from Erbil.
Around 500 French soldiers are based in Iraq, where they advise the Peshmerga and train Iraqi elite forces in Baghdad. About 5,000 US troops are in Iraq.
— Iraq Live Update (@IraqLiveUpdate) October 2, 2015
US defence officials stressed Daesh drones would have zero strategic impact on the upcoming battle to retake control of Mosul from Daesh.
"The implications of this are certainly not an existential threat and not something that's militarily significant in that it's going to stop anything that needs to happen from happening," Dorrian said.
The unnamed defence official said the biggest implication was guidance being issued across the coalition to not pick up any drones.
"Treat them as unexploded ordnance," he said.
"You see a drone sitting on the ground, don't pick it up," and call a bomb disposal expert, he added.