Al Qaeda's chief called upon the group's militants to kidnap westerners for prisoner swaps, according to the monitoring service SITE Intelligence Group Sunday. Ayman al-Zawahiri appeared in an audio interview, where he said the kidnappings could help secure the release of jailed jihadists.

In the recording posted online Al-Zawahiri called for kidnappings "until they liberate the last Muslim male prisoner and last Muslim female prisoner in the prisons of the Crusaders, apostates, and enemies of Islam," via Reuters. The report from the news agency stated it was not able to verify the authenticity of the recording. 

Al-Zawahiri, speaking in Arabic, reportedly called kidnappings a "powerful weapon in the fight against the enemy." It's believed al-Zawahiri is hiding out in near the Afghanistan-Pakistan border.

In a May report about the elusive leader of Al-Qaeda, NBC News noted that he has survived at least four assassination attempts but there hasn't been an attempt that has come close since 2007. He's apparently gone to great lengths to avoid being detected, even using green-screen technology to disguise his living conditions when posting video messages. 

Al-Zawahiri was the right-hand man to Osama Bin Laden. He co-founded the extremist group and was believed to be a crucial player in the planning of the terrorist attacks on 9/11 that killed nearly 3,000 people in the United States. Al-Zawahiri served as the group's most visible face after the attacks. He became the leader of Al Qaeda shortly after Bin Laden was killed in Abbottabad, Pakistan, by a group of U.S. Navy SEALS in 2011.

Al-Qaeda has been greatly weakened over the years as U.S. forces have killed key figures within the group.

"The core al Qaeda — the group that is now led by Ayman al-Zawahiri — is not what it used to be," CIA Director John Brennan told NBC News. "But it did take quite a bit of patience and time and a deliberate and focused years-long effort for us to be able to say that we really have taken off of the battlefield much of al Qaeda's capabilities."