A small quadcopter drone was shot down with a Patriot missile, which usually cost around $3m (£2.5m), a US general has said.
General David Perkins told a military symposium "a very close ally" used the surface-to-air missile to bring down the drone.
"They shot it down with a Patriot missile," the general said, in comments shared by the US Army on YouTube. "Now that worked, they got it, okay, and we love Patriot missiles."
Patriots are radar-guided missiles designed to shoot down enemy missiles, travelling at five times the speed of sound to strike its target.
The general added: "That Quadcopter that cost $200 from Amazon.com did not stand a chance against the Patriot."
However, he questioned the economic consequences of the strategy.
"I'm not sure that's a good economic exchange ratio," he said.
"If I'm the enemy, I'm thinking, 'hey, I'm going to get on eBay and buy as many of these $300 quadcopters as I can and expend all the Patriot missiles out there'."
While General Perkins did not give any further details about the strike, he said the unnamed country was "dealing with an adversary," suggesting it was not a test.
Colin Bull, a research consultant with software testing company SQS, said using the expensive missile was "overkill and potentially ineffective."
He said: "If drones fall in to the wrong hands, there’s currently nothing to stop someone flying a payload laden drone into restricted airspace, without action such as this taking place.
"Rather than using expensive military resources to deal with potentially rogue drones, implementing regulation and the standardisation of radio frequencies, on which drones operate, is vital to combat such threats.
"Ultimately, this makes it easier for security teams to use jamming devices to stop a suspect drone from entering the space."
He warned: "Despite the obvious benefits of drones, they must be embraced and feared in equal measures.
"They might look pretty innocent, but on closer inspection, what you find can be terrifying. Putting it bluntly, these devices are in fact a flying payload system with the ability to deliver anything, including incendiary devices or grenades."
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