( CNN ) -- Familiar terrorist groups , familiar threats , familiar boasts and grievances -- all in new messages tied , either directly or indirectly , to al Qaeda . Two videos and one audio link have come to light in recent days that suggest that the world 's most recognizable terrorist group is still active , at least in online postings . The audio is a question-and-answer session purportedly involving al Qaeda leader Ayman al-Zawahiri that was published Friday on the radical Islamist website Hanein . While CNN has not verified the authenticity of the tape , the voice is similar to al-Zawahiri 's from previously authenticated recordings . In a wide-ranging , nearly hour-long interview with al Qaeda 's media arm , known as al-Sahab , al-Zawahiri touches on everything from drones to Syria to Egypt . He insists that al Qaeda is holding strong 13 years after the United States launched its `` war on terror '' following the September 11 , 2001 , attacks . `` The upper hand is for the one who does not withdraw from his land , '' al-Zawahiri says . `` Who has withdrawn from Iraq , and who has not ? Who has withdrawn from Afghanistan and who has not ? '' Al-Zawahiri adds that even U.S. President Barack Obama knows al Qaeda `` is expanding . '' `` Al Qaeda is scattered in all the Islamic world and among the oppressed , '' he said . That analysis is relatively peaceful compared with the chilling words uttered in a newly discovered video from Al-Shabaab . Among its threats : `` We will blow you up , until we finish you off . '' Members of the Somalia-based , al Qaeda-linked militant group also use the video to reflect on one of its most memorable , deadliest attacks to date -- the four-day siege last September of an upscale Nairobi , Kenya , indoor shopping center that ended with at least 67 killed . That Westgate Mall attack may have been one of the bloodiest tied to Al-Shabaab , but it wo n't be the last , men featured on the video suggested . `` It 's not that Westgate was enough , '' they say . `` There are still hundreds of men who are wishing for such an operation . '' Peter Bergen , an authority on terrorism who interviewed the late Osama bin Laden and is a CNN national security analyst , said that this Al-Shabaab threat has to be taken seriously . `` We certainly ca n't dismiss their ability to carry out those kinds of terrorist attacks , '' Bergen said . The two messages come on the heels of another one that got attention this week showing what looks like the largest and most dangerous gathering of al Qaeda in years . In the middle of that video clip , the man known as al Qaeda 's crown prince , Nasir al-Wuhayshi , appears brazenly out in the open , greeting followers in Yemen . Al-Wuhayshi is the No . 2 leader of al Qaeda globally and the head of al Qaeda in the Arabian Peninsula , or AQAP , which is considered the most dangerous al Qaeda affiliate . In a speech to the group , al-Wuhayshi makes it clear that he 's going after the United States , saying `` We must eliminate the cross . ... The bearer of the cross is America ! '' The video started appearing on jihadist websites recently , drawing the attention of U.S. officials and global terrorism experts . U.S. officials say they believe it 's authentic . They believe the highly produced video is recent . With some fighters ' faces blurred , there is worry it signals a new round of plotting .
Al Qaeda 's Ayman al-Zawahiri purportedly answers questions on range of subjects . He says that even President Obama knows al Qaeda `` is expanding '' A new Al-Shabaab video threatens more bloody attacks like the Nairobi mall siege . A different video shows an apparent meeting of al Qaeda leaders in Yemen .