A British-accented militant who has appeared in beheading videos released by the ISIS group in Syria over the past few months bears "striking similarities" to a man who grew up in London, a Muslim lobbying group said on Thursday.

Mohammed Emwazi has been identified by news organisations as the masked militant more commonly known as "Jihadi John.

"Research director Asim Qureshi from London-based CAGE, which works with Muslims in conflict with British intelligence services, said on Thursday that he saw strong similarities, but because of the hood worn by the militant, "there was no way he could be a hundred percent certain."

According to The Washington Post and the BBC, Emwazi was born in Kuwait, grew up in west London and studied computer programming at the University of Westminster.

The university confirmed that a student of that name graduated in 2009.Qureshi said Emwazi first contacted CAGE in 2009.

Emwazi said he had travelled to Tanzania with two other men after leaving university, but was deported and questioned in Amsterdam by British and Dutch intelligence services.

The following year, Emwazi accused British intelligence services of preventing him from travelling to the country of his birth, Kuwait, where he planned to marry.

CAGE quoted an email Emwazi had sent saying, "I had a job waiting for me and marriage to get started. But now I feel like a prisoner, only not in a cage, in London."

"The Mohammed that I knew was extremely kind, extremely gentle, extremely soft-spoken, was the most humble young person that I knew," Qureshi said.

He said he hadn't had contact with Emwazi since January 2012.Qureshi accused British authorities of alienating and radicalising young British Muslims with heavy-handed policies.

"When we treat people as if they are outsiders, they will inevitably feel like outsiders," he said.