The hunt for the Islamic State militant who beheaded U.S. journalist Jim Foley is focusing on British jihadists, including a one-time British rapper known as L Jinny.
The Islamic State group has attracted hundreds of Western followers, including some 500 Britons and 100 Americans.
L Jinny, whose real name is Abdel-Majed Abdel Bary, is believed to be one of them.
His father, Adel Abdel Bary, thought to have been a close associate of Osama bin Laden, was extradited on terrorism charges to the United States.
Photos of L Jinny posted on social media sites show a skinny young man sporting a goatee.
British intelligence agencies have been working around the clock to identify the man with a British accent who took a knife to Foley's throat in a video the extremist group released last week.
Although the killer's face was masked with a black hood on the video, his voice and British accent can clearly be heard. Intelligence agencies are said to be using sophisticated voice recognition and surveillance technology to identify the killer.
A German rapper known as Deso Dogg also is believed to have joined the extremist group.