Iraq security agencies are working to verify the authenticity of a video that purportedly shows the elusive leader of the Sunni extremist group that has declared an Islamic state in a large chunk of territory it controls leading prayers this week in northern Iraq, authorities said.

The video said to show Abu Bakr al-Baghdadi, the head of the Islamic State group, was reportedly filmed on Friday at the Great Mosque in Iraq's second-largest city, Mosul. It was posted on at least two websites known to be used by the organization and bore the logo of its media arm.

The sermon in Mosul would the first public appearance for al-Baghdadi, a shadowy figure who has emerged as perhaps the preeminent figure in the international jihadi community. Al-Baghdadi, who has a $10 million U.S. bounty on his head, took over the group four years ago and has since transformed it from an al-Qaida affiliate focused on Iraq into an independent transnational force that controls of a huge stretch of land straddling the Syria-Iraq border.

Iraqi military spokesman Lt. Gen. Qassim al-Moussawi told reporters Sunday the country's security services are still analyzing the 21-minute video to verify whether the speaker is indeed al-Baghdadi, and that the government will "announce the details once they are available."

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

Wearing black robes and a black turban, the man in the video said to be al-Baghdadi urges his followers to jihad, and emphasizes the implementation of a strict interpretation of Islamic law. He strikes an almost humble tone, telling listeners: "I am not better than you or more virtuous than you."

A senior Iraqi intelligence official told The Associated Press on Saturday that an initial analysis indicated that the man in the video is indeed al-Baghdadi. The official spoke on condition of anonymity because he was not authorized to brief the media.

The government carried out at least three airstrikes Sunday in Mosul, two of which hit the Rashidiyah neighborhood and one of which targeted the 17 Tammuz district, residents said. It was not clear whether the raids were related to the video.

A medical official in the city said seven people were killed and 30 wounded in one strike in Rashidiyah. Casualty figures were not immediately available for the other air raids.

Both the residents and the official spoke on condition of anonymity over fears for their safety.

It was not clear what the air raids targeted, and the Iraqi military could not immediately be reached for comment.

Over the past month, al-Baghdadi's fighters have overrun much of northern and western Iraq, adding to the territory they already control in neighboring Syria. The group's initial surge in Iraq has crested, at least for now, after having grabbed most of Iraq's predominantly Sunni Arab regions and reaching majority Shiite areas, where resistance is tougher.

One of the main battlefronts now is the country's largest oil refinery near Beiji, some 250 kilometers (155 miles) north of Baghdad, where government forces are besieged by Islamic State group fighters.

Al-Moussawi, the military spokesman, said security forces repelled an overnight attack on the facility, killing around 20 militants and damaging eight vehicles. The casualty figures could not be independently verified.

The Sunni militant offensive has ramped up the pressure on Iraq's political leaders to quickly form a new government that can confront the insurgents and keep the country from fracturing along ethnic and sectarian lines.

Prime Minister Nouri al-Maliki, a Shiite whose State of Law bloc won the biggest chunk of the vote in April elections, is angling for a third consecutive term, and vowed last week he would not withdraw his candidacy — despite calls for him to step aside.

He has been widely accused of trying to monopolize power. Rivals and former allies alike say he has exacerbated the crisis by failing to pursue reconciliation with the country's Sunni minority, which complains it is treated like second-class citizens by al-Maliki's government.

Late Saturday, Shiite cleric Muqtada al-Sadr said the next prime minister must come from State of Law, but he urged the bloc to put forward a candidate other than al-Maliki, saying an alternative nominee "will help end the suffering."

"It is necessary to demonstrate the national and paternal spirit for a higher and noble goal," al-Sadr said in a statement released by his office. "I mean changing the candidates, which will be a welcome and blessed step during this hard time the country goes through."

The comments marked a shift in al-Sadr's position. He previously said that the next prime minister must be Shiite, but not from State of Law.

The political group that al-Sadr used to head controls 33 out of the 328 seats in parliament. Al-Maliki's bloc holds 92.

Also, Iran's state news agency said an Iranian pilot named Shoja'at Alamdari Mourjani was killed while defending Shiite holy sites in the Iraqi city of Samarra, which is home to one of the most revered shrines in Shiite Islam. It said Mourjani was buried Friday in a village near Shiraz in southern Iran.

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It was not clear in what capacity Mourjani was fighting in Iraq, nor how he was killed.

Iran, the regional Shiite power, has said it will provide any help necessary to aid Iraq in its current crisis. Tehran has maintained close ties with successive Shiite-led governments in Iraq since the 2003 ouster of Saddam Hussein, a Sunni who oppressed the Shiites.