Updated

Al Qaeda's No. 2 leader, Ayman al-Zawahiri, presented an eulogy for a slain Afghan Taliban commander in a new audiotape released Tuesday, according to a transcript issued by a U.S. group that monitors militant messages.

The SITE Institute, based in Washington, did not say how it had obtained the audiotape, but it has been known to obtain copies of Al Qaeda messages before their release.

The new tape's authenticity could not independently be confirmed, but a militant Web site that usually gives forward notice of Al Qaeda messages had announced earlier Tuesday that a tape would be coming from Al-Zawahiri.

In the tape, the deputy Al Qaeda leader offers condolences to the Taliban for the loss of Mullah Dadullah, a one-legged commander who orchestrated suicide attacks and beheadings before dying of gunshot wounds in a U.S.-led operation on May 12 in southern Afghanistan.

"The martyrdom of the commander of the martyrdom-seekers, Mulla Dadullah (may Allah have mercy on him), shall break the back of the Crusaders and their helpers in Afghanistan and hasten their imminent defeat," al-Zawahiri was quoted as saying in a transcript provided by SITE of the six-minute, 23-second audiotape.

Al-Zawahiri praised Dadullah for having remained "in the midst of his troops, leading the campaign of attack against the Crusaders and their helpers to cleanse the soil of Afghanistan from their filth."

He compared the Taliban commander's death to that of Al Qaeda in Iraq leader Abu Musab al-Zarqawi, also killed by U.S.-led forces, and said it would hasten the insurgents' victory.

Al-Zawahiri said Dadullah was a "martyr" who had "prepared, equipped and left behind him hundreds of martyrdom-seekers who impatiently await the order to swoop down" on U.S.-led and Afghan government forces.

Most of Al Qaeda's leadership, including al-Zawahiri, is believed to have sought refuge in a mountainous zone on the Afghanistan-Pakistan border since the Taliban was ousted from power by a U.S.-led offensive in late 2001.