Russia tested a nuclear-capable drone submarine, according to Pentagon officials.
U.S. intelligence agencies noticed the test of the vehicle, which the Pentagon code-named "Kanyon," when it launched from a Sarov-class submarine on Nov. 27, The Washington Free Beacon reports.
Pentagon spokesman Capt. Jeff Davis would not give the Free Beacon a comment on the matter.
"We closely monitor Russian underwater military developments, but we will not comment specifically about them," he said.
The Free Beacon first reported on the drone sub in September 2015. The Russian military confirmed the project, which they call the "Ocean Multipurpose System 'Status-6,'" two months later, saying the program had been unintentionally disclosed.
"The Status-6, a nuclear powered, nuclear armed drone submarine, is the most irresponsible nuclear weapons program that Putin's Russia has come up with," former Pentagon official Mark Schneider told the Free Beacon.
"Status-6 is designed to kill civilians by massive blast and fallout."
Magnus Nordenman, director of the trans-Atlantic security initiative of the Atlantic Council, warned in an April interview with The New York Times that the U.S. and their allies were not competing with Russia in submarine technology.
"In the Russian naval structure, submarines are the crown jewels for naval combat power," Nordenman said. "The U.S. and NATO haven't focused on anti-submarine operations lately, and they've let that skill deteriorate."