A man purporting to be the leader of the Sunni extremist group that has declared an Islamic state in territory it controls in Iraq and Syria has made what would be his first public appearance, delivering a sermon at a mosque in Iraq's second-largest city, according to a video posted online on Saturday.

The 21-minute video that is said to show Abu Bakr al-Baghdadi, the head of the Islamic State group, was reportedly filmed on Friday at the Great Mosque in the northern city of Mosul. It was released on at least two websites known to be used by the organisation and bore the logo of its media arm, but it was not possible to independently verify whether the person shown was indeed al-Baghdadi.

There are only a few known photographs of al-Baghdadi, an ambitious Iraqi militant believed to be in his early 40s with a $10m US bounty on his head. Since taking the reins of the group in 2010, he has transformed it from a local branch of al-Qaida into an independent transnational military force, positioning himself as a dominant figure in the global jihadi community.

Al-Baghdadi's purported appearance in Mosul, a city of some 2 million that the militants seized last month, came five days after his group declared the establishment of an Islamic state, or caliphate, in the territories it seized in Iraq and Syria. The group proclaimed al-Baghdadi the leader of its state and demanded that all Muslims pledge allegiance to him.

In the video, the man said to be al-Baghdadi says that "the mujahedeen have been rewarded victory by God after years of jihad, and they were able to achieve their aim and hurried to announce the caliphate and choose the Imam", referring to the leader.

"It is a burden to accept this responsibility to be in charge of you," he adds. "I am not better than you or more virtuous than you. If you see me on the right path, help me. If you see me on the wrong path, advise me and halt me. And obey me as far as I obey God."

Speaking in classical Arabic with little emotion, he outlines a vision that emphasises holy war, the implementation of a strict interpretation of Islamic law, and the philosophy that the establishment of an Islamic caliphate is a duty incumbent on all Muslims.

He is dressed in black robes and a black turban, a sign that he claims descent from the prophet Muhammad. He has dark eyes, thick eyebrows and a full black beard with streaks of grey on the sides.

During the video the camera pans away to show several dozen men and boys standing for prayer in the mosque, and a black flag of the Islamic State group hangs along one wall. One man stands guard, with a gun holster under his arm.

Aymenn al-Tamimi, an expert on militant factions in Syria and Iraq, said al-Baghdadi had come under some criticism since unilaterally declaring the establishment of a caliphate, in part for not appearing before the people.

"He had declared himself caliph, he couldn't hide away. He had to make an appearance at some time," al-Tamimi said. Traditionally, a Muslim ruler is expected to live among the people, and to preach the sermon before communal Friday prayers.

The brazenness of his purported appearance – before dozens of people, and made public only a day after its occurrence – suggested the Islamic State's confidence in its rule of Mosul.

"The fact that he has done this without any consequences in Mosul's biggest mosque is a sign of [the Islamic State group's] power within the city," said al-Tamimi. He said it would be likely to boost the morale of al-Baghdadi's fighters, and deal a blow to the group's rivals.

A senior Iraqi intelligence official said that after an initial analysis the man in the video was believed to indeed be al-Baghdadi. The official said the arrival of a large convoy in Mosul around midday on Friday coincided with the blocking of mobile phone networks in the area. He says the signal returned after the convoy departed.

The official spoke on condition of anonymity because he was not authorised to brief the media.

A Mosul resident confirmed that mobile networks were down around the time of Friday prayers, and then returned a few hours later. He spoke on condition of anonymity because of fears for his safety.

Another aspect of the rule al-Baghdadi envisions was made clear in a series of images that emerged online late on Saturday showing the destruction of at least 10 ancient shrines and Shia mosques in territory his group controls.

The 21 photographs posted on a website that frequently carries official statements from the Islamic State group document the destruction in Mosul and the town of Tal Afar. Some of the photos show bulldozers ploughing through walls, while others show explosives demolishing the buildings.

Residents from both Mosul and Tal Afar confirmed the destruction of the sites.



