US-led troops in Afghanistan continue to search for al-Qaeda insurgents
Little is certain about the identity of the "double agent" behind last week's bombing of a CIA base in Afghanistan, named by the US media as Humam Khalil Abu-Mulal al-Balawi - even his exact name is a mystery.
A source associated with the Pakistani Taliban identified the suicide bomber as Humam Khalil Mohammed, a 36-year-old Jordanian doctor and al-Qaeda sympathiser.
He is said to come from Zarqa, the same Jordanian town as Abu Musab al-Zarqawi, the leader of al-Qaeda in Iraq who was killed in an airstrike by coalition forces in June 2006.
Western sources say Balawi was recruited by the Jordanian intelligence services to infiltrate al-Qaeda's senior circles.
They add because of his medical background, he could have been recruited to find the whereabouts of Ayman al-Zawahri, the Egyptian doctor who is al-Qaeda's deputy leader.
When his relatives and friends in Zarqa found out about the attack, they said that they believed he had been travelling to Turkey to continue his medical studies.
Instead, Balawi gained the trust of both the Jordanian intelligence service, one of the CIA's most useful allies in the Middle East, and the CIA itself, with a string of useful intelligence leads.
A former US counter-terrorism officer told the
newspaper that Balawi had been someone "who had already worked with us" providing "actionable intelligence" during several weeks of undercover work along the Afghanistan-Pakistan border.
Balawi was therefore able to penetrate the CIA base in Khost, eastern Afghanistan, last week, with explosives strapped to his body.
Killing seven staff, the attack was the deadliest the CIA had suffered in more than 25 years.
A former CIA official told the
New York Times
newspaper that the fact militants could carry out an attack using a double agent showed their strength, in spite of US drone aircraft missile attacks on suspected militants in neighbouring Pakistan.
"The fact that they can pull this off shows that they are not really on the run," he said.
But the mystery does not end there.
He had grown up in Kuwait, with a Palestinian background, before his family moved to Jordan in 1990 when Saddam Hussein invaded.
His family describe him as a devout Muslim, someone who cared for the poor, but was a bit aloof.
But several reports say Balawi had an online persona using the pseudonym Abu Dujana al-Khorasani.
He is said to have made several postings on jihadist sites.
In one of them he describes himself as originally from the north of the Arabian peninsula, married with two daughters.
He describes how he rose through the ranks of militants, outlining his support for violent opposition to the US-led operations in Iraq and Afghanistan.
Jarret Brachman, author of Global Jihadism: Theory and Practice and terrorism consultant to the US government said Humam al-Balawi had been an influential voice on the web.
"He is the top five jihadists," Brachman told the New York Times. "He's one of the biggest guns out there."
And according to the SITE Monitoring Service, a watch group that translates messages found on extremist forums, "Khorasani" had been a prolific contributor to jihadist websites for more than two years.
While the mystery remains, questions will undoubtedly be asked as to how Balawi managed to infiltrate so deeply, and work so closely with high-ranking officials of the CIA.