A video posted online purports to show the leader of the Islamic State extremist group delivering a sermon at a mosque in the northern Iraqi city of Mosul.
Abu Bakr al-Baghdadi has almost never been seen in public, and there are only a few known photographs of him.
The video was released on a website known to be used by the group, but it was not possible to independently verify whether the person shown was indeed al-Baghdadi.
Last month, the Islamic State, formerly known as the Islamic State of Iraq and Syria (ISIS), declared a new caliphate and instated Abu Bakr as the caliph - the head of state.
In the video, the man who is purported to be al-Baghdadi lays out the group's agenda, and the philosophy of the rule in its self-declared caliphate.
He is dressed in black robes and a black turban, has dark eyes, thick eyebrows and a full black beard. He speaks eloquent classical Arabic, but with little emotion.
"God has granted your brothers, the Mujahideen, victory and a conquest after years of patience and holy struggle, and enabled them to achieve their objective," Baghdadi said, according to the recording.
"And they have rushed to declare an Islamic caliphate and to appoint an imam (leader), which is a duty for Muslims, a duty that had been lost for centuries that had been absent from reality, making many Muslims ignorant of it," he added.
"I have been afflicted by this great affair, I have been afflicted by this trust, a heavy trust," the man said. "I was appointed in charge of you, though I am not the best or better than you, so if you see me in the right, then help me, and if you see me in the wrong, advise me and put me right."
In an audio tape, Baghdadi last week called on Muslims worldwide to take up arms and flock to the 'caliphate' it has declared on captured Syrian and Iraqi soil.
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