"He's thought to have played a key role in the attack on December 30 at Khost."

The Khost bombing, the second-most deadly in the history of the CIA, was carried out by a double agent linked to al-Qaeda who was recruited by Jordanian intelligence.

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Taliban arrest motives questioned

The US official said al-Yemeni who was in his late 20s or early 30s had forged links to al-Qaeda's branch in Yemen, the Haqqani network and the Afghan and Pakistan Taliban.

Al-Yemeni's death "would be the latest victory in a systematic campaign that has pounded al-Qaeda and its allies, depriving them of leaders, plotters, and fighters," added the official.

The news came as Leon Panetta, the CIA director, said in an interview that aggressive attacks against al-Qaeda fighters in Pakistan had driven the network's leaders into hiding and left the organisation in disarray.

"It's pretty clear from all the intelligence we are getting that they are having a very difficult time putting together any kind of command and control, that they are scrambling. And that we really do have them on the run," he told the Washington Post in an interview published on its website on Wednesday.

On Wednesday another suspected US drone attack in North Waziristan killed at least nine fighters, according to intelligence officials and residents, when missiles hit the vehicles they were travelling in.

Security officials said missiles fired from a pilotless aircraft hit the main town of Miran Shah followed Madakhel, about 40 kilometres west, about 50 minutes later.

The remote North Waziristan province is a refuge for Taliban and al-Qaeda fighters, and other armed groups, from where they launch attacks both within Pakistan and neighbouring Afghanistan.

The US does not publically talk about drone strikes but such incidents occur regularly, targeting Taliban commanders in Pakistan's semi-autonomous tribal belt, which Washington calls the global headquarters of al-Qaeda.