The man viewed as Al-Qaeda's No. 3 leader, Mustafa Abu al-Yazid, is reported to have been killed.
U.S. officials, speaking on condition of anonymity, said there was strong reason to believe that Yazid was killed in a U.S. drone attack in Pakistan's tribal areas in the past two weeks. They described Yazid as the organization's "chief operating officer," "with a hand in everything from finances to operational planning."
The Egyptian-born militant, a longtime member of Al-Qaeda, was described as the organization's "prime conduit" to leader Osama bin Laden and his deputy, Ayman al-Zawahri.
Islamist websites quoted a statement from the terrorist network as saying Yazid, also known as Sheikh Said al-Masri, had died along with members of his family.
He has been reported killed before, but this is the first time Al-Qaeda has acknowledged such claims on the Internet.
'No One Irreplaceable'
Analysts and officials are divided as to the impact his death would have on the network.
Rahimullah Yousafzai, a senior Pakistani journalist based in Peshawar, describes Yazid's death as a "huge loss" for Al-Qaeda, "because he had stayed here [in the region] for a long time, had organized the movement, and he knew many people here."
Afghan President Hamid Karzai's spokesman, Wahid Omar, welcomed the reports that Yazid had been killed, but added, "We are not sure of any significant impact of the killing of one of the members of Al-Qaeda."
Germany-based journalist Souad Mekhennet, who covers terrorism issues for "The New York Times," tells RFE/RL's Radio Mashaal that Yazid's death would be "a tough case" for Al-Qaeda.
But she says a number of other Al-Qaeda leaders considered third-in-command have been killed or captured in recent years -- and that has not translated into a weakening of the group's fighting resolve.
"Al-Yazid was someone who was responsible for the military actions inside the group and he also was the link between the top leadership and other groups," Mekhennet says. "So, yes, he was a key figure, but no one is irreplaceable [in Al-Qaeda] so there will be someone who is going to replace him."
A message from Al-Qaeda posted on Islamist forums said Yazid had been killed along with his wife, three daughters, a grandchild, and other men, women, and children.
The SITE group, which monitors Islamist websites, said the message did not say how or where he was killed but that it was dated May.
The message, which described Yazid as the organization's top commander in Afghanistan, spoke of his "martyrdom."
"His death will only be a severe curse by his life upon the infidels," it said.
There's been no official confirmation of Yazid's death from Islamabad. But the AP news agency quoted unidentified Pakistani intelligence officials as saying Yazid died in a missile strike in North Waziristan on May 21. They said their sources had not seen Yazid's body and did not know where he was buried.
Reuters news agency said that attack targeted a house owned by a tribesman near Miranshah, the main town in North Waziristan, a militant stronghold bordering Afghanistan. Intelligence officials at the time said six militants were killed but residents said 12 people, including four women and two children, died.
Imprisoned Over Sadat Assassination
Yazid, 54, was a former member of Egypt's Islamic Jihad -- one of the groups that went on to form Al-Qaeda -- and spent time in prison over the 1981 assassination of Egyptian President Anwar Sadat.
In the late 1980s, Yazid turned up in Afghanistan. He later followed bin Laden to Sudan and back to Afghanistan, where he was believed to have served as Al-Qaeda's chief financial officer, managing the finances for the September 11, 2001, attacks in New York and Washington.
Yazid emerged in 2007 as the "official in charge" of the terrorist movement's operations in Afghanistan.
Yazid's last public statement was released on May 4, eulogizing the two top Al-Qaeda leaders in Iraq (Abu Omar al-Baghdadi and Abu Ayub al-Masri) who were killed in April.
written by Antoine Blua, with contribution from Radio Mashaal's Majeed Babar and agency reports