"Jihadi John", the masked Islamic State militant linked to the beheading of Western hostages, was named on Thursday as Kuwaiti-born London computer programmer Mohammed Emwazi by experts and the media.
The International Center for the Study of Radicalization at London's King's College, a leading resource for studying foreign jihadists, said it believed the identity "to be accurate and correct".
"The fact that 'Jihadi John' has been unveiled in this manner demonstrates that whatever efforts are made, the ability to mask one's identity is limited or in fact impossible, and their true identities will eventually be revealed," it said in a statement.
But London's Metropolitan Police would not confirm a report that first appeared in the Washington Post, which identified the suspect as Emwazi, who grew up in west London after moving to Britain aged six.
"We are not going to confirm the identity of anyone at this stage," Richard Walton, head of the police Counter Terrorism Command, said in a statement.
Emwazi, believed to be in his mid-20s, was identified to the Washington Post by friends and others familiar with the case, with one close acquaintance telling the paper: "I have no doubt that Mohammed is Jihadi John".
The suspect is from a middle class family and earned a degree in computer programming before traveling to Syria around 2012, according to the report.
He apparently became radicalized after being detained by authorities following a flight to Tanzania and being accused by British intelligence officers of trying to make his way to Somalia, where they believed he had links to a man with connections to the jihadist militant group al-Shabab.
The suspect was also angered after being barred from flying from London to Kuwait, according to emails sent by him to pressure group Cage.
"I had a job waiting for me and marriage to get started," he wrote in a June 2010 email published by the Washington Post and the Guardian.
But now "I feel like a prisoner, only not in a cage, in London," he added. "A person imprisoned and controlled by security service men, stopping me from living my new life in my birthplace and country, Kuwait."
He is described as being quiet and polite with a taste for stylish clothes.
Contacted by AFP, the interior ministry could not immediately comment on the reports.
British media had previously suggested he could be a different British jihadist.
"Jihadi John", named after Beatle John Lennon due to his British accent, is believed to be responsible for the murders of US journalists James Foley and Steven Sotloff, British aid workers David Haines and Allan Henning and American aid worker Abdul-Rahman Kassig.
He also appeared in a video with the Japanese hostages Haruna Yukawa and Kenji Goto, shortly before they were killed.
In the videos posted online, he appears dressed all in black with only his eyes exposed, and wields a knife while launching tirades against the West.
British intelligence officers estimate that there are around 700 homegrown militants fighting for IS in Syria and Iraq.