An al-Qaeda chemical and biological weapons expert may have been among six people killed in a suspected US missile strike on a Pakistani madrassa near the Afghan border today, according to security officials.

Abu Khabab al-Masri, also known as Midhat Mursi al-Sayid Umar, was an Egyptian chemist regarded as one of al-Qaeda’s top bomb makers and had a $5 million bounty on his head.

Pakistani security officials said he was the target of a pre-dawn attack that destroyed a house close to a madrassa used by militants about 12 miles west of Wana, the main town in the tribal region of South Waziristan.

The officials said they had heard that al-Misri, 55, was killed but had been unable to check the reports as it was hard to reach the area, a haven of al-Qaeda and Taleban militants. Similar reports in 2006 turned out to be unfounded.

The attack came just before Yousaf Raza Gilani, Pakistan’s new Prime Minister, was due to meet President Bush in Washington for talks focusing on co-operation in the War on Terror.

The United States, alarmed by rising casualties among Nato forces in Afghanistan, has been pressing Pakistan to do more to combat the Islamic militants who have been sheltering in its tribal areas since 2001.

But Pakistan’s Government is reluctant to inflict further casualties on its armed forces, anger its predominantly Muslim population, and damage relations with the ethnic Pashtun tribes who inhabit the borderlands.

So in recent months, the US military has stepped up its missile attacks, many using unmanned Predator drones, on militant targets in Pakistan, prompting protests from Islamabad.

Al-Masri is described by the website of the US Government Rewards for Justice programme, which offered the bounty, as an “explosives expert and poisons trainer working on behalf of Al-Qaeda”.

He served as a trainer at Al-Qaeda’s Derunta camp in Afghanistan when it was set up in the late 1990s “where he provided hundreds of mujahedin with hands-on training in the use of poisons and explosives”, the site said.

“Since 1999, he has distributed training manuals that contain instructions for making chemical and biological weapons. Some of these training manuals were recovered by US forces in Afghanistan,” it said.

The site said his exact whereabouts were unknown but that he might be living in Pakistan.

Residents of the area where he was said to have been killed said they heard the sound of a drone aircraft engine, suggesting that the missile may have been fired by a Predator.

Spokesmen for Nato and US-led coalition forces in Afghanistan denied involvement in any cross-border strike, but said they could not speak for the CIA, which also operates drones.

Pakistan’s military spokesman said he had little information, and noted that US coalition forces were no longer informing the Pakistan army about every missile strike.

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