(CNN) -- Al Qaeda has claimed responsibility for the suicide bombing in Afghanistan last month that killed seven CIA employees and contractors and a Jordanian military officer, according to a statement posted on Islamist Web sites.
Mustafa Abu Yazid, al Qaeda's commander of operations in Afghanistan and its No. 3 man, said the attack avenged the death of Baitullah Mehsud, leader of the Taliban in Pakistan who was killed in a missile strike last August, and al Qaeda operatives Saleh al-Somali and Abdullah al-Libi.
The December 30 blast at a U.S. base in Khost, in southeastern Afghanistan, killed seven CIA operatives including two from private security firm Xe, formerly known as Blackwater. The eighth victim was Jordanian Army Capt. Sharif Ali bin Zeid, a cousin of Jordan's King Abdullah II.
A former U.S. intelligence official identified the suicide bomber as Humam Khalil Abu-Mulal al-Balawi, a Jordanian doctor who acted as a double agent. He was recruited as a counterterrorism intelligence source, according to a senior Jordanian official.
U.S. sources said bin Zeid was the Jordanian operative working closely with al-Balawi, who was from the same hometown as the onetime leader of al Qaeda in Iraq, Abu Musab al-Zarqawi.
Jordanian and U.S. intelligence agencies apparently believed that al-Balawi had been rehabilitated from his extremist views and were using him to hunt Ayman al-Zawahiri, al Qaeda's No. 2 figure, the former intelligence official said.