A web posting Thursday said Zawahri has assumed responsibility for the group, and that there will be no shift in al-Qaida policy. The post said the decision was taken by the general leadership of the group.

    An associate of bin Laden's since the 1980s, he has been described as the organizational mastermind（出谋划策的人） of the operation, complementing bin Laden's inspirational and financial role.

    Zawahri released a message earlier this month acknowledging bin Laden's death.  In it, he vowed to continue the path of jihad to expel what he called invaders of Muslim land and to purify it from injustice.

    Zawahri, a doctor from a well-to-do Cairo family, first focused his anger on the Egyptian government. He led a militant group there before joining forces with al-Qaida, with its broader focus, in the late 1990s.

    His June 8 message reaffirmed the group's focus of anti-Americanism.

    Zawahri said that America is not facing an individual or group, but what he termed a rebelling nation awakening to a jihadist renaissance.

    Al-Qaida has been largely sidelined during the popular uprisings that have swept the Arab world in recent months, which for the most part have been calls for political and democratic change. But the organization's offshoot al-Qaida in the Arabian Peninsula has appeared to gain ground during the unrest.

    The Yemen-based group had already begun to overshadow the original, with active plots against Western targets and a charismatic leader in Anwar al-Awlaki, even before its adherents captured more territory recently in the politically-unstable Arabian nation.

    That could be one of the main challenges facing Zawahri. He is described as soft-spoken and rigidly dogmatic by fellow Islamists.  Moreover, with counter-terrorism efforts greatly limiting al-Qaida's organizational efforts - Zawahri's strength - it has had to rely more on exporting ideas to adherents, usually through bin Laden.

    Mohamed Salah, a political analyst with the London-based al-Hayat newspaper, says he expects to see Zawahri intensify his use of the media, through audio or video messages, to fill the void.  Whether he will inspire similar loyalty is unclear.

    But as for the loss of bin Laden's ability to provide for al-Qaida financially, Salah believes that the organization has long been running on very meagre resources.

    Added to that, he argues, Zawahri's close contacts with the key Egyptian members of al-Qaida make him bin Laden's natural heir.(本文由在线英语听力室整理编辑)