BAGHDAD — Wearing a black turban and black robes, the leader of the self-proclaimed Islamic state that stretches across eastern Syria and much of northern and western Iraq made a startling public appearance, his first in many years, at a well-known mosque in the Iraqi city of Mosul, according to a video released on Saturday whose contents were confirmed by experts and witnesses.
Until then, there had been very few photographs on the Internet of the insurgent known as Abu Bakr al-Baghdadi, the leader of the Islamic State in Iraq and Syria, or ISIS. But on Friday he delivered a public sermon in a city once under American control with an audacity that even Osama bin Laden never tried.
ISIS released a 21-minute video of the sermon on Saturday.
Previously he had been all but invisible, seemingly reluctant to risk a public appearance as his group grew in strength and he became the United States’ second-most sought-after terrorist, after Ayman al-Zawahri, the leader of Al Qaeda. The United States government has offered a $10 million reward for information leading to his capture.
But on Friday at the pulpit of Mosul’s Great Mosque, Mr. Baghdadi appeared confident, calm and measured as he urged the faithful to fast during Ramadan and undertake jihad. He also asserted his position as caliph, or spiritual leader, of the Muslim faithful, calling himself “Khalifa Ibrahim,” or caliph Abraham, a reference to the prophet Abraham, who appears in the Quran. Mr. Baghdadi’s militant group declared its territory in Iraq and Syria a caliphate, or Islamic state, on June 29.
“Do jihad in the cause of God, incite the believers and be patient in the face of this hardship,” he admonished the congregation. “If you knew about the reward and dignity in this world and the hereafter through jihad, then none of you would delay in doing it.”
ISIS militants took over Mosul, Iraq’s second-largest city, on June 10, after the Iraqi Army fled. ISIS fighters patrol the streets, although far fewer than in the first days after the takeover, and while some people have gone back to work, the city is far from normal. The congregation at the mosque in the video had been ordered to come to Friday Prayer, said a man who was there but who asked not to be identified for fear of retribution.
When worshipers arrived at the mosque, they were searched thoroughly by armed ISIS fighters, and the congregants were told where and how to sit, said the man. No one was allowed to leave until 10 minutes after the end of Mr. Baghdadi’s sermon, the man said.
The sermon was no extemporaneous cameo, but a carefully crafted speech in which he asked for the congregation’s support and struck an almost humble and pious tone that was difficult to square with the group’s tactics on the ground, which include kidnapping for ransom, summary executions and beheadings.
“I was placed as your caretaker, and I am not better than you,” he said, according to a translation by SITE Intelligence Group, which monitors extremist activity online. “So if you found me to be right, then help me, and if you found me to be wrong, then advise me and make me right.”
“I do not promise you, as the kings and rulers promise their followers and congregation, luxury, security and relaxation; instead, I promise you what Allah promised his faithful worshipers,” he said.
Mr. Baghdadi’s address appeared to be aimed at several audiences, analysts said. He seemed to be appealing to followers of other militant groups in Syria and Iraq to join ISIS, and also to Iraqi Sunnis to look to him as a leader rather than the Iraqi government.
Daniel Benjamin, a senior counterterrorism official in the State Department from 2009 to 2012, said that if the video was authentic, Mr. Baghdadi’s appearance would be a “remarkable event.”
“If Baghdadi has emerged from hiding, it suggests that he is adopting a posture as a different kind of leader from Osama bin Laden, Ayman al-Zawahri and the like, and by implication a greater one,” said Mr. Benjamin, now a scholar at Dartmouth College. “He is demonstrating that ISIS has what they didn’t: territory that is secure, and he is its ruler.”
“As a public demonstration of leadership, you’d have to go back to April 1996, when Mullah Omar appeared on top of a building in Kandahar in a cloak that was said to belong to the prophet and was declared commander of the faithful,” Mr. Benjamin added.
Peter Neumann, a professor of security studies at Kings College London, said the appearance was “a sign of confidence” and a “message to all these other jihadists, this is really happening, it’s not going to go away anytime soon.”
The video was still being authenticated late Saturday by the Central Intelligence Agency. A spokesman for the Iraqi Interior Ministry, Brig. Gen. Saad Maan, told Reuters that the ministry thought it was fake, but Mr. Neumann said he had little doubt that it was authentic, in part because ISIS would have little to gain from a falsified video. An American official who spent extensive time in Iraq said that the man in the video appeared to be Mr. Baghdadi.
Two people who were in the mosque when Mr. Baghdadi spoke said they had no question it was him. But they had never seen him before, so their certainty was based primarily on how the ISIS fighters treated him.
Also on Saturday, official Iranian news agencies reported that an Iranian pilot had been killed in fighting in Iraq, which appeared to be the first confirmation of the deployment of Iranian forces there. There have been unconfirmed reports that Iran had sent military advisers and jets to Iraq.The Islamic Republic News Agency said that the pilot, Col. Shoja’at Alamdari, was killed in Samarra defending a Shiite shrine. The Fars News Agency said that he was a member of the Islamic Revolutionary Guards Corps.
The agencies provided no further details about his death, and it was not clear whether he died on the ground or in the air. There have been no reports of planes shot down by the rebels.
An Iraqi employee of The New York Times contributed reporting from Mosul, Michael R. Gordon from Washington, and Thomas Erdbrink from Tehran.