Baghdadi hailed the jihadi "victory" that he said had restored the caliphate after centuries.
"God gave your mujahideen brothers victory after long years of jihad and patience ... so they declared the caliphate and placed the caliph in charge. This is a duty that has been lost for centuries."
He added: "Allah likes us to kill his enemies and make jihad in his sake."
Baghdadi also discussed practical matters, calling called 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 Islamic State - formerly the Islamic State of Iraq and al-Sham - into the world's richest terrorist group, all the while carefully staying out of the public view. There are only two known photographs of al-Baghdadi, one dating from his 2005-2009 imprisonment in a United States detention camp in Iraq. On his release, to be handed over to Iraqi control, he reportedly told US officials: "I'll see you in New York".
Title seen as 'null and void'
Isis' self-declared caliphate faces a growing a backlash from leading Muslim figures. Yesterday, leading Sunni Muslim scholar Yusef al-Qaradawi denounced the proclamation, saying that it was in violation of sharia.
Qaradawi, a Qatar-based preacher who is regarded as a spiritual guide of the Muslim Brotherhood in his native Egypt, said that the move had "dangerous consequences" for Iraqi Sunnis and the conflict in Syria.
"We look forward to the coming ... of the caliphate," he said, referring to the form of pan-Muslim government last seen under the Ottoman Empire. He added: "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 said the declaration, and the nomination of Baghdadi as caliph, by a group "known for its atrocities" fail to meet strict conditions dictated by sharia.
The title of caliph, he said, can "only be given by the entire Muslim nation", not by a single group.
Others decried 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," Sheikh Abbas Shuman, his representative, said.
Rebels in Syria, who have turned on the jihadists that hijacked the uprising against Bashar al-Assad, have branded the caliphate announcement as "null and void".
It was even denounced by the Jordanian cleric Abu Mohammed al-Maqdessi, the mentor of al-Qaeda in Iraq's late leader Abu Musab al-Zarqawi.
About the caliphate
1. By declaring the establishment of an Islamic caliphate, Isis is claiming to be the successor of the political and religious community established by the Prophet Muhammad.
2. The caliphate is a powerful ideal - the concept of a nation of Muslims worldwide ruled by sharia law under a caliph who holds both spiritual and secular authority.
3. There have been many caliphates over Islam's 1400-year history, with the greatest Muslim empires ruling from Morocco to Central Asia.
4. The caliphate institution lost its authority centuries ago, becoming a tool of secular rulers to gain religious backing. It was formally abolished in 1920 by Turkey's secular founder Mustafa Kamal Ataturk.
5. While many Muslims long for the unified community of the Prophet's era, only a radical fringe are likely to see Isis as its heir.
- AP
