Attorney General Eric Holder revealed Tuesday that President Barack Obama ordered American airstrikes against the Khorasan Group in Syria because the shadowy al-Qaida offshoot was close to launching attacks on the United States or its allies. The group's plotting led to a tightening of air travel restrictions this past summer, Holder said.

While most Americans had never heard of that band of Islamist extremists prior to the sustained overnight bombing campaign, “this is a group that has been known to us for two years,” Holder told Yahoo Global News Anchor Katie Couric.

“We hit them last night out of a concern that they were getting close to an execution date of some of the plans that we have seen,” he said. “And the hitting that we did last night, I think, will probably continue until we are at a stage where we think we have degraded their ability to get at our allies or to the homeland.”

U.S. officials told Yahoo News that the Khorasan terror plot involved American and European aircraft. Holder did not confirm that but linked the group directly to Homeland Security Secretary Jeh Johnson’s decision in early July to forbid uncharged cellphones, laptops, and other electronic devices on some U.S.-bound flights originating overseas.

"I can say that the enhanced security measures that we took [in] the aviation sector some months ago," Holder told Couric, "[were] based on concerns we had about what the Khorasan Group was planning to do."

The Khorasan Group comprises “seasoned” or “veteran” al-Qaida fighters from Afghanistan, Pakistan, and Yemen, according to U.S. officials. It is thought to be led by a man so close to Osama bin Laden that he was told about the terrorist strikes of Sept. 11, 2001, before they happened.

Members of the group converged on Syria, forged links with militant rebel groups, and worked to enlist Westerners, including Americans, for “external operations” — attacks made possible by the new recruits’ European or U.S. passports.

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Its members were “constructing and testing improvised explosive devices,” one official said.

“We were monitoring active plotting that posed an imminent threat to the U.S. and potentially our allies,” one senior official told reporters at a background briefing. “That was the united view of our intelligence community.”

“It was a threefold perfect storm,” added one U.S. counterterrorism official, describing the intelligence that prompted Obama to order the airstrikes that pounded Khorasan Group facilities in Syria overnight.

U.S. officials had picked up intelligence that the plot to attack Western aircraft had reached advanced stages and “there were timetables on it,” one official told Yahoo News.

It was this intelligence that led to Monday night’s strike — using Tomahawk missiles and precision bombs — on Khorasan training camps, munitions facilities, and command and control centers west of Aleppo. The strikes also targeted Khorasan’s leader, Muhsin al-Fadhli, a 5-foot-5 Kuwaiti-born militant who formerly led al-Qaida in Iran.

But while U.S. officials told reporters that the strikes had been effective in hitting their targets, they could not confirm whether they had gotten al-Fadhli. U.S. officials have offered a $7 million reward for any information that led to his capture.

The comments today about a possibly imminent attack by Khorasan were especially striking since they appeared to contradict repeated assurances from senior U.S. government officials in recent weeks denying there was any specific or credible information about any plots against the U.S. homeland.

Until last week, when Director of National Intelligence James Clapper first referred to Khorasan as a “potential” threat, there had been few public references to it.

Obama had never said the group’s name in public before his brief remarks Tuesday about the overnight U.S.-led onslaught against Islamic State targets in Syria.

“We also took strikes to disrupt plotting against the United States and our allies by seasoned al-Qaida operatives in Syria who are known as the Khorasan Group,” Obama said on the South Lawn of the White House. “And once again, it must be clear to anyone who would plot against America and try to do Americans harm that we will not tolerate safe havens for terrorists who threaten our people.”

U.S. officials told Yahoo News that they first picked up intelligence two years ago about Khorasan Group operatives moving into Syria and forging links with the al-Nusra Front, another Syrian rebel group that was aligned with al-Qaida. As first reported by Yahoo News, National Counterterrorism Center Director Matthew Olsen alluded to the group — but not by name — last July when he told the Aspen Security Forum that veteran al-Qaida operatives had moved into Syria for the purpose of taking advantage of the country’s civil war to mount attacks against the U.S.

“In some cases this is essentially the same cast of characters that we’ve had our eye on for many years. These are known operatives to us rather than a new group appearing out of whole cloth,” a senior administration official told reporters on a conference call arranged by the White House.

The United States had been contemplating striking the extremist cell “separate and apart from the growing threat from ISIL,” as the militant group Islamic State is also known, the official said. “Clearly the fact of the United States launching a military action in Syria provided an opportunity to take that action.”

A senior U.S. official also confirmed to Yahoo News Tuesday that there were “communications” between the Khorasan operatives and members in Yemen of al-Qaida in the Arabian Peninsula, the terror group that has most alarmed U.S. officials because of its advanced bomb-making capabilities.

Al-Fadhli was first designated as a global terrorist by the U.S. Treasury Department in 2005. At the time, U.S. officials linked him to terror plots dating back to October 2002 involving attacks to blow up the French ship MV Limburg against U.S. Marines based on Failaka Island in Kuwait.

But he was also described as a key terrorist financier, providing financial and material support to both al-Qaida and the network of Abu Musab al-Zarqawi, the original leader of al-Qaida in Iraq, the group that has since morphed into the Islamic State.

Al-Fadhli was again designated by the Treasury Department in December 2012. This time, officials described him as a top member of al-Qaida’s network operating in Iran, helping to facilitate the flow of fighters and money through that country. Although al-Fadhli was at one point arrested by the Iranians, he was later released. In one of the early hints of his involvement in the Syria conflict, Treasury officials said then that his network was “working to move fighters and money through Turkey to support” al-Qaida elements in Syria. He also was “leveraging his extensive network of Kuwaiti jihadist donors to send money to Syria via Turkey.”

Amid concern in Washington that the group could recruit Americans, Holder told Yahoo News that the United States and its allies would soon unveil a new approach to tagging potential terrorist threats among citizens returning home after fighting alongside jihadis overseas.

”It will be focused on people who have terrorist connections and come up with new ways in which information is shared between INTERPOL members that, frankly, don’t exist now,” he said. “We have red notices that we use for people who are charged with crimes. But we’re gonna come up with a new kind of notice that deals with people who are suspected of engaging in terrorist activities.”