The shadowy Islamist group in Syria known as Khorasan was in the "execution stage of a plot" when it was targeted by U.S. airstrikes this week, Attorney General Eric Holder said Friday.
"I can't get into specifics, but there is no question that the Khorasan Group had moved into the execution phase of a plot," Holder told NBC's Pete Williams. "And the bombing campaign that was begun was designed to disrupt and stop that plot that was imminent."
The Al-Qaeda-connected group was virtually unknown to Americans before the U.S. began military strikes on Monday night, though sources say the group has long been known to the Obama administration and Congress.
At least one senior member of the Khorasan Group was believed to have been killed in the strikes, The Washington Post reported, but there was no confirmation from U.S. officials.
"We'd been following them for two years, and we have watched as they have progressed," Holder told NBC. "We were concerned that they had gotten to the point where they were in a position to execute one plot that they had been working on for some time."
The Obama administration's top aviation security official echoed similar comments Friday, saying Khorasan presents "a clear and present danger" to U.S. and European commercial flights.
The group has been researching and testing improvised explosive devices for use aboard airliners, John Pistole, head of the Transportation Security Administration said, according to the Associated Press.
"The stakes are real and the threats are high," Pistole told the Washington Aero Club. "I see the Khorasan Group as being a very capable, determined enemy who was very much focused on getting somebody or something on a plane bound for Europe or the United States."