His story is the stuff of spy fiction: an undercover agent who used guile and technology to help the CIA find a top al-Qaeda leader. But if true, newly published claims by a self-professed Danish double agent could complicate efforts by U.S. and European spy agencies to penetrate terrorist groups in the future, intelligence experts say.

Morten Storm, an admitted former jihadist, sparked a controversy in his native country this week with a newspaper interview claiming he helped the CIA target Anwar al-Awlaki, the al-Qaeda leader who was killed in a drone strike last year. The 36-year-old Dane offered a detailed account of how he cultivated a years-long relationship with the U.S.-born propagandist in Yemen, and then helped the CIA plant the tracking device that led to Awlaki’s death.

Both the CIA and the Danish intelligence service declined to confirm or deny the account. But Storm has buttressed his version of events by supplying a Danish newspaper with copies of purported e-mail exchanges with Awlaki, as well as what he says is a secret audio recording of a meeting with a CIA officer last year in which the targeting of Awlaki was discussed.

Storm did not reply to e-mails and phone messages requesting comment. But several U.S. and European analysts — including former intelligence officers — have described his account as broadly plausible while acknowledging that it may be impossible to verify many of the specific claims.

Whether true or not, analysts say, Storm’s boast of undercover service for the Danish and U.S. intelligence agencies could exacerbate security concerns in Denmark, a country that has been repeatedly targeted by al-Qaeda in recent years.

Moreover, his detailed depiction of the Awlaki manhunt could make it harder for Western governments to place moles inside terrorist groups, spy agency veterans and terrorism experts say. Of particular concern is Storm’s description of the use of ordinary-looking USB thumb drives as a homing device for CIA missiles.

“This is worrying, and it should be,” said Magnus Ranstorp, a Swedish scholar and former adviser on counterterrorism to the European Union. “At the very least, it is operationally embarrassing, and one has to wonder what will come out next.”

Storm’s “outing” of himself as an informant began this week with the posting of an interview on the Web site of Jyllands-Posten, a Danish newspaper. In the interview and accompanying articles, the former motorcycle gang member describes his evolution in the past decade from an anti-American Islamic radical to an undercover spy intent on destroying Awlaki, a Muslim cleric he once admired.

“He was my sheikh, he was my teacher, he was a friend of mine,” Storm says of Awlaki in the recorded conversation with a purported CIA officer identified only as “Michael.” He adds that, because of “the evil in him,” Storm agreed to help the Americans find and kill Awlaki, then a top leader in the al-Qaeda affiliate in Yemen.

By his own account, Storm’s association with radical Islamic causes and figures drew the attention of European investigators in the mid-2000s. But in 2006, he agreed to become an informant for the the Danish Security and Intelligence Service.

He claimed in the interview to have befriended Awlaki over several trips to Yemen, and says the al-Qaeda leader sometimes asked him to purchase perfume and other personal items for Awlaki’s wife. The two men sometimes exchanged messages using thumb drives delivered by couriers, a practice that would later make it easy for Storm to provide Awlaki with a cleverly disguised homing device.

Storm said he decided to go public with his story because he believed he had not been properly credited for helping the CIA eliminate Awlaki in September 2011. Experts speculated that the secretly recorded audio tape was Storm’s attempt to secure a CIA acknowledgment of his role in the agency’s hunt for Awlaki. In the recording, the individual identified as Michael thanks Storm for his contributions but also cites a “parallel” CIA effort that he says was more directly responsible for Awlaki’s slaying.

Former intelligence officers say Storm’s detailed description and supporting evidence suggest that he was working as informant, although he may have embellished certain details. Bruce Riedel, a former CIA officer and counterterrorism adviser to the White House, said the Dane appeared to be “the classic model for penetrating al-Qaeda: a European convert to Islam married to a Yemeni Muslim with a fondness for jihad.”

But Storm’s willingness to go public illustrates the risks inherent in using double agents, said Robert Baer, a former CIA case officer who served in the Middle East.

“When they walk out the door, they can do a lot of damage,” Baer said. “It’s an utter nightmare.”

Julie Tate contributed to this report.