Claim: Iraqi Terror Leader's First Appearance in Video

The shadowy and rarely-photographed leader of the ultra-violent jihadi group the Islamic State was alleged to have appeared for the first time publicly in a video today, delivering a fiery sermon at a mosque in the Iraqi city of Mosul, which his fighters had taken and occupied this month in a brutal offensive.

Abu Bakr al-Baghdadi, the nom de guerre of the extremist militants' leader Khalifah Ibrahim, made his dramatic debut dressed head to foot in black, with a bushy black beard streaked with gray.

Intelligence agencies analyzing the 21-minute video told ABC News they could not immediately verify that the man in the ISIS video released by its al-Furqan media wing was al-Baghdadi.

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But his face resembled the two known photos of him -- grainy headshots -- on U.S. wanted posters offering a $10 million bounty. The video also was an official IS release and promoted by the terror group.

Forensic analysis of terror leaders appearing on video is an arduous and not immediate process. One private analyst said it is unlikely to be a hoax or stand-in for al-Baghdadi, whose fighters blitzed Iraqi government troops in the north last month and have seized towns and cities such as Mosul and institute the harshest Islamic law.

'You can't be the leader of the un-free world without showing your face at some point,' author J.M. Berger, who closely tracks jihadi social media and IS, told ABC News today. 'If you want to be a head of state and inspire people, you have to show up in public.'

Berger said he had been monitoring tweets by rank and file IS fighters in Iraq in recent days, who reported that their figurehead had given a talk in Mosul. 'It's being heavily promoted by IS social media,' he added.

The Islamic State announced June 29 that it had formed a 'caliphate' from northern Syria through a swath of northern Iraq, naming al-Baghdadi as 'Caliph,' the leader. The group was previously known as ISIS or ISIL.

But Iraqi news media have reported in the past week that al-Baghdadi may have been wounded or killed in airstrikes in Mosul. His stunning and well-choreographed emergence at Friday prayers yesterday -- using multiple camera angles to capture his sermon -- may have been a convincing attempt to offer proof of life.

'I was cursed with this great endeavor... Obey me in my obedience to God, disobey me if I disobey God,' al-Baghdadi thundered in Arabic from the pulpit in Mosul's central mosque.

Most of his talk was centered on the holy period of Ramadan and fasting, as well as supplications to God. Al-Baghdadi only devoted five minutes to his proclamation of the caliphate in an effort to legitimize IS.

He also took a shot at other jihadist movements that have not rallied behind him, claiming that establishing an Islamic caliphate was an 'obligation that has been squandered for centuries.'

Al-Baghdadi has for years carefully avoided the spotlight, ensuring his personal security by only releasing sporadic audio statements -- unlike his predecessor Abu Musab al-Zarqawi, who led IS when it was called al Qaeda-Iraq.

The late Osama Bin Laden's al Qaeda, now led by Ayman al-Zawahiri -- who is believed to be hiding in Pakistan -- has been at war with al-Baghdadi's IS in Syria through its proxy force, Jabhat al-Nusra. This year, al Qaeda-core and IS disavowed each other over its growing disputes.

In a final scene in the IS video, al-Baghdadi is shown leading prayers before hundreds in the mosque, including fighters whose figures are blurred out to protect their identities. Several AK-47s can be seen leaning against the pulpit.