As Al-Qaeda rebuilds in Pakistan's tribal areas, a new generation of leaders has emerged under Osama bin Laden to cement control over the network's operations, the New York Times reported on Monday.
The new leaders rose from within the organisation after the death or capture of the operatives that built Al-Qaeda before the September 11, 2001 attacks, it said citing American intelligence and counter-terrorism officials.
This has led to surprise and dismay within United States intelligence agencies about the group's ability to rebound from an American-led offensive, the influential daily said.
It has been known that American officials were focusing on a band of Al-Qaeda training camps in Pakistan's remote mountains, but a clearer picture is emerging about those who are running the camps and thought to be involved in plotting attacks.
American, European and Pakistani authorities have for months been piecing together a picture of the new leadership, based in part on evidence gathered during terrorism investigations in the past two years, it said.
Particularly important have been interrogations of suspects and material evidence connected to a plot British and American investigators said they averted last summer to destroy multiple commercial airlines after takeoff from London, the Times said.
Intelligence officials also have learned new information about Al-Qaeda's structure through intercepted communications between operatives in Pakistan's tribal areas, although officials said the group has a complex network of human couriers to evade electronic eavesdropping.
The investigation into the airline plot has led officials to conclude that an Egyptian paramilitary commander called Abu Ubaidah al-Masri was the Qaeda operative in Pakistan orchestrating the attack, the Times said citing unnamed officials.
Masri, a veteran of wars in Afghanistan, is believed to travel frequently over the rugged border between Pakistan and Afghanistan.
He was long thought to be in charge of militia operations in Kunar province of Afghanistan, but he emerged as one of Al-Qaeda's senior operatives after the death of Abu Hamza Rabia, another Egyptian who was killed by a missile strike in Pakistan in 2005.
The Times cited officials as saying the evidence that was accumulating about Masri and a handful of other Qaeda figures has led to a reassessment within the American intelligence community about the strength of the group's core in Pakistan's tribal areas, and its role in some of the most significant terrorism plots of the past two years, including the airline plot and the suicide attacks in London in July 2005 that killed 56.
Although the core leadership was weakened in the counter-terrorism campaign begun after the Sep 11 attacks, intelligence officials now believe it was not as crippling as once thought.
That reassessment has brought new urgency to joint Pakistani and American intelligence operations in Pakistan and strengthened officials' belief that dismantling Al-Qaeda's infrastructure there could disrupt nascent large-scale terrorist plots that may already be under way, the Times said.
Officials cited by the daily say they believe that, in contrast with the somewhat hierarchical structure of Al-Qaeda in Afghanistan before Sep 11, the group's leadership is now more diffuse, with several planning hubs working autonomously and not reliant on constant contact with bin Laden and Ayman al-Zawahri, his deputy.
Much is still not known about the backgrounds of the new Qaeda leaders; some have adopted nom de guerre. Officials and outside analysts cited by the Times said they tend to be in their mid-30s and have years of battlefield experience fighting in places like Afghanistan and Chechnya.
They are more diverse than the earlier group of leaders, which was made up largely of battle-hardened Egyptian operatives. American officials cited by the Times said the new cadre includes several Pakistani and North African operatives.
It cited experts as saying they still see Al-Qaeda in Mesopotamia as largely independent of Al-Qaeda's hub in Pakistan but that they believe the fighting in Iraq will produce future Qaeda leaders.
American officials say they still know little about how operatives communicate with bin Laden and Zawahri.
"There has to be some kind of communication up the line, we just don't see it," one senior intelligence official cited by the Times said.
American counter-terrorism officials said they did not believe that any one figure had taken over the role once held by Khalid Shaikh Mohammed, the operations chief who was arrested in Pakistan in 2003 and is being held at Guantánamo Bay, Cuba.
During a recent legal hearing, Mohammed, a Pakistani national claimed responsibility for planning dozens of attacks over more than a decade.
Despite the damage to the structure of Al-Qaeda after the Sep 11 attacks, concern is still high that the group is determined to attack globally, the Times said citing "top American officials".