The claim was made by Mustafa Abu Yazid, al-Qaida commander in Afghanistan, in a statement posted on an Islamic Web site, CNN reported Thursday. Several other groups have made similar claims.
The seven employees of the U.S. Central Intelligence Agency were killed in the Dec. 30 suicide bomb attack in Afghanistan's Khost province along with a Jordanian Army Capt. Sharif Ali bin Zeid, CNN said. Baitullah Mehsud died in a drone attack last August.
The statement said the suicide bomb attack also avenged the deaths of al-Qaida operatives Saleh al-Somali and Abdullah al-Libi.
A U.S. intelligence official identified the suicide bomber as Humam Khalil Abu-Mulal al-Balawi, a Jordanian doctor and a double agent, who was being used to locate Ayman al-Zawahiri, al-Qaida's No. 2 man after Osama bin Laden, the report said.
The al-Qaida statement identified al-Balawi as Hamam Khalil Mohammed Abu Malal, alias Abu Dujana Khorasani, a well-known Islamist author and a preacher on jihadi Web sites, CNN reported.
"We ask God to bless the people who follow your path, Abu Dujana," it said, adding his followers will not "have peace of mind until they slaughter the Americans."
CNN quoted some analysts that militant groups may be vying to take credit for the killings to attract money and new recruits.