Islamic State leader Abu Bakr al-Baghdadi addresses Muslims in Mosul

Notoriously secretive head of the organisation formerly known as Isis comes out of hiding to lead Friday prayers as "Caliph Ibrahim"

Abu Bakr al-Baghdadi, the leader of the Islamic State, emerged from the shadows to lead Friday prayers at Mosul’s Great Mosque, calling on the world’s Muslims to “obey” him as the head of the caliphate declared by the Sunni jihadist group.

The notoriously secretive jihadi, who has never before been seen in public, chose the first Friday prayer service of Ramadan to make an audacious display of power in the city that the Sunni Islamists have now controlled for three weeks.

Speaking from the balcony in his new incarnation as self-anointed “Caliph Ibrahim”, Baghdadi announced himself as “the leader who presides over you”, urging Muslims to join him and "make jihad" for the sake of Allah.

Under his direction, the Islamic world would be returned to “dignity, might, rights and leadership”, he said.

“I am the wali (leader) who presides over you, though I am not the best of you, so if you see that I am right, assist me,” he said, dressed in a black turban and robe reminiscent of the last caliphs to rule from Baghdad.

“If you see that I am wrong, advise me and put me on the right track, and obey me as long as I obey God in you.”

Al-Baghdadi hailed the jihadi “victory” which he said had restored the caliphate after centuries.

“God gave your mujahedeen brothers victory after long years of jihad and patience... so they declared the caliphate and placed the caliph in charge,” he said.

“This is a duty on Muslims that has been lost for centuries.”

In the address - which spread rapidly across jihadi websites with translations in multiple languages - al-Baghdadi also discussed practical matters, calling for doctors, judges, engineers and experts in Islamic jurisprudence to help develop the caliphate.

It was a bold move from a man who has turned his breakaway al-Qaeda faction, until recently known as Isis, into the world’s richest terrorist group but all the while carefully kept himself out of the public view.

There are only two known photographs of al-Baghdadi, one dating from his 2005-2009 imprisonment in a US detention camp in Iraq. On his release, to be handed over to Iraqi control, he reportedly remarked to US officials: “I’ll see you in New York”. And with that parting shot, he disappeared from sight - until now.

His appearance came just as Iraqi officials claimed that he had been severely injured in a raid by government forces in Anbar province and had since fled to Syria. Instead, he was coming out of hiding in the heart of Iraq’s second city, laying claim to an empire and attempting to demonstrate the might of the Islamic State in the territories it has wrested from Baghdad’s control.

On Saturday the Iraqi government denied that the man in the video was al-Baghdadi, sticking by its claim that he had been wounded in a military operation.

Brigadier General Saad Maan, an Interior Ministry spokesman, told Reuters that the footage was "indisputably" not of him. "We have analysed the footage ... and found it is a farce," he said.

The Islamic State’s self-declared caliphate faces a growing a backlash from leading Muslim figures. On Saturday, the prominent Sunni Muslim scholar Yusef al-Qaradawi denounced the proclamation, saying that it was in violation of sharia law.

Mr Qaradawi, a Qatar-based scholar who is regarded as a spiritual guide of the Muslim Brotherhood in his native Egypt, said in a statement that the move had “dangerous consequences” for Iraqi Sunnis and the conflict in Syria.

“We look forward to the coming, as soon as possible, of the caliphate,” he said, referring to the form of pan-Muslim government last seen under the Ottoman Empire.

“But the declaration issued by the Islamic State is void under sharia and has dangerous consequences for the Sunnis in Iraq and for the revolt in Syria,” he added.

He said the declaration, and the nomination of al-Baghdadi as caliph, by a group “known for its atrocities and radical views” fail to meet strict conditions dictated by sharia law.

The title of caliph, he said, can “only be given by the entire Muslim nation”, not by a single group.

Others decried the Islamic State - formerly known as the Islamic State of Iraq and al-Sham (Isis) - as terrorists.

The Grand Imam of Al-Azhar, regarded by many to be the leading authority on Sunni Islamic thought, “believes that all those who are today speaking of an Islamic State are terrorists,” his representative, Sheikh Abbas Shuman, told AFP earlier this week.

“The Islamic caliphate can’t be restored by force. Occupying a country and killing half of its population... this is not an Islamic state, this is terrorism,” he said.

Rebels in Syria, who have turned on the jihadists that hijacked the uprising against Bashar al-Assad and appalled many by their brutality, have branded the caliphate announcement as “null and void”.

It was even denounced by the Jordanian cleric Abu Mohammed al-Maqdessi, the former mentor of Al-Qaeda in Iraq’s late leader Abu Musab al-Zarqawi. He warned it would only lead to more violence.