A top al-Qaeda explosives expert was the main target of the US spy-drone attack in Pakistan last weekend and not the British terrorism suspect who also apparently died in the strike, intelligence sources have told The Times.

Abu Zubair al-Masri, an Egyptian described as being “high up in the al-Qaeda pecking order”, was understood to have been holding an operational meeting with four other key figures, including Rashid Rauf, the British-Pakistani terror suspect, when three Hellfire missiles were fired at their thick-walled compound in the village of Ali Khel, about ten miles from the Afghan-Pakistan border.

British intelligence officials indicated that it had been a strictly US operation and that the tip-off – from the Pakistanis – about five suspected al-Qaeda operatives in the compound in North Waziristan had required an instant response.

The apparent lack of prior knowledge on the part of the British, however, raised concerns about embarrassing gaps in intelligence-sharing between the CIA and MI6. Al-Masri is thought to be one of the most senior al-Qaeda members to be killed this year. The sources said it was most likely that he was the principle reason for the attack and that it may not have been known that Rauf was also present. Al-Masri – one of several known al-Qaeda members to bear the name, which means “the Egyptian” – was described as being close to Osama bin Laden and his deputy Ayman al-Zawahiri, also an Egyptian.

The killing of al-Masri, and reportedly of Rauf, was the latest in a surge of drone strikes being linked to an attempt by President Bush to make serious inroads into al-Qaeda before he leaves office. There are also fears in Washington of a terrorist spectacular to test Barack Obama early on.

“Absolutely this is from the top, absolutely this is about legacy,” a former intelligence official close to the decision-making process said.

“But there is also a very real threat of an attack in Obama’s first days and even the bitterest loser wouldn’t want to see that. It would be this Administration’s ‘fault’.”

Mr Bush signed off on new rules of engagement this summer allowing missile strikes to be launched with a much lower probability of success – about 50 per cent against 90 per cent previously. US Predators and the larger Reaper unmanned drones, which are armed with Hellfire missiles and precision bombs, have stepped up their strikes into Pakistan’s border areas in the past three months.

Western officials believe that al-Qaeda has been forced to move senior leaders out of the tribal areas as a result. An attack near the town of Bannu last Thursday was the first in the settled areas of North West Frontier Province, outside the lawless tribal agencies that have been the centre of al-Qaeda and Pakistani Taleban activity. The attack killed five people including a Saudi Arabian national, according to Pakistani officials.

A senior Western diplomat said that the Bannu strike had been aimed at al-Zawahiri. Bin Laden’s deputy has long been believed to be in the tribal areas, although several previous strikes occurred further north in the Bajaur region and Pakistani intelligence continues to place him there. The policy appears to have the blessing of the Pakistani Government, despite its public displays of fury. Under the arrangement, the US has carte blanche to attack foreign al-Qaeda fighters in the tribal areas, while Pakistan takes responsibility for tackling Pakistani and Afghan militants.

The increase in US attacks follows the redeployment from Iraq of several drones since the summer. US forces are constructing new bases from which to fly the unmanned aircraft, close to the Pakistan border. The latest drones are believed to be a variant of the Reaper, which has voice-recognition technology allowing it to attack insurgents based on monitored phone conversations.

MI6 is to write to the parliamentary Intelligence and Security Committee, chaired by Kim Howells, the former Labour Foreign Office Minister, to explain its position in relation to the weekend attack – the first time that a British citizen has been reportedly killed by an American unmanned drone. Under British intelligence rules, neither MI6 nor MI5 is authorised to carry out assassinations.

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