ISIS has expanded its repertoire of killing methods, apparently using an explosives-laden drone in Iraq.
The terror group attacked a Kurdish defensive post on October 2 using a drone carrying "some sort of explosives," a senior Peshmerga officer said.
The drone killed two Peshmerga soldiers and injured two French military personnel north of Mosul, the Peshmerga officer said.
Images of the drone's remnants show "it appears to be a cheap Chinese drone, easily available on the market," CNN's Ben Wedeman said from Irbil, Iraq.
"This is, to the best of our knowledge, the first time that ISIS uses a drone as an explosive device. And it certainly is cause for concern given how easy it is to obtain a simple, cheap drone and load it ... with explosives."
Col. John Dorrian, spokesman for the US-led coalition fighting ISIS, said ISIS has used drones in the past.
"We've seen several reports about ISIS' use of commercial off-the-shelf drones, including instances where they've used these capabilities to deliver explosives. It's a threat that's not new to the area," Dorrian told reporters Wednesday.
"Now, most of these are just surveillance and not ... dropping ordinance or this latest sort of Trojan horse-style attack."
Unlike the typical surveillance drones, this drone exploded after local forces picked it up for inspection, Dorrian said.
While exploding drones are "certainly not an existential threat" and "aren't having any kind of strategic impact at all," the coalition is still taking precautions against ISIS drones, Dorrian said.
"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," he said.
Dorrian said a system called Drone Defender and others are capable of detecting, identifying, tracking and defeating drone threats.
The deadly drone explosion happened about 30 kilometers (18 miles) north of Mosul, ISIS' most important bastion in Iraq.
International forces are plotting a mission to reclaim Mosul, but tensions between Turkey and Iraq -- two US allies in the fight -- could undermine recent gains in the battle against ISIS.