DUBAI (Reuters) - Al Qaeda’s Afghan wing has claimed last week’s attack at a U.S. base in Afghanistan in which a double agent turned suicide bomber killed seven CIA officers, saying the attack was revenge for the deaths of their leaders.

A U.S. Marine from India Company, 3rd Battalion 4th Marines, passes by Afghan boy as he patrols in the small town of Delaram in Helmand province, southern Afghanistan January 6, 2010. REUTERS/Marko Djurica

“He detonated his explosive belt, concealed from the eyes of those who do not believe in the Hereafter, in a gathering of American and Jordanian intelligence men,” Mustafa Abul-Yazid, the leader of al-Qaeda in Afghanistan, said in a statement posted on a website on Thursday used by al-Qaeda linked organizations.

The suicide bombing, the second-most deadly attack in CIA history, followed a failed attempt to blow up a Detroit-bound plane on Christmas Day.

Former intelligence officials have said Humam Khalil Abu-Mulal al-Balawi, a doctor, was recruited by Jordanian intelligence to try to infiltrate al Qaeda and the Taliban.

Balawi had associated with Islamists in the past, but U.S. and Jordanian spy agencies thought that Balawi had been successfully “de-radicalized.”

The bombing took place inside Forward Operating Base Chapman, a well-fortified compound in Khost province near the southeastern border with Pakistan.

“He avenged our prime martyrs, and as he wrote in his final testament, may God have mercy on him: Taking revenge for the leader the Amir Beitullah Mehsud and the leaders Abu Saleh al-Somali and Abdallah Said al-Libi and their brothers, may God have mercy on them.”

Mehsud, the leader of the Taliban Movement of Pakistan, was killed by a missile-firing U.S. drone aircraft in South Waziristan in August.

CIA agents at the base helped oversee strikes against Taliban and al Qaeda targets along the border between Afghanistan and Pakistan, according to former intelligence officials.

The security breach was a major setback to the CIA, which has been expanding its presence in Afghanistan.

Eight CIA employees were among those killed in a bombing of the U.S. Embassy in Beirut in 1983.