(CNN) In an audio message posted online Thursday, a man purported to be al Qaeda leader Ayman al-Zawahiri pledges allegiance to new Taliban leader Mullah Akhtar Mohammad Mansour.

"As a leader of al Qaeda jihadi group, we announce our allegiance to you," the voice says in the message.

CNN couldn't independently verify the message's authenticity.

The Taliban, the Sunni Islamist group that took over much of Afghanistan in the 1990s, named Mansour its leader last month after confirming its previous leader, Mullah Mohammed Omar , was dead.

A U.S.-led 2001 invasion booted the Taliban from power after it offered safe haven to al Qaeda leader Osama bin Laden, but a Taliban insurgency continues in Afghanistan to this day.