BAGHDAD, Iraq (CNN) -- The U.S. military in Iraq denied widespread reports Friday that trumpeted the capture of a top Iraqi insurgent leader.
Skeptical of the reports at first, the U.S. military is now certain that Abu Ayyub al-Masri -- the head of al Qaeda in Iraq -- has not been captured, a senior U.S. military official told CNN.
The reports emerged late Thursday that the elusive militant had been detained in the northern city of Mosul.
That's where U.S. and Iraqi forces have been fighting the predominantly Sunni al Qaeda in Iraq -- which has a strong presence in the city. Mosul has been called the group's last strong urban bastion in Iraq.
The report of his capture was first made by the Iraqi media and then picked up by The Associated Press.
The news spread throughout the country. An imam at a Shiite mosque in Baghdad was heard praising the arrest during his sermon at Friday prayers. Watch more about al-Masri's role with al Qaeda in Iraq
But U.S. military and intelligence officials were surprised and skeptical, despite the insistence of Iraqi officials that al-Masri was already in U.S. military custody.
Al-Masri , called "the Egyptian" and also known as Abu Hamza al-Muhajer, took the reins of Iraq's al Qaeda offshoot in June 2006, after a U.S. missile strike killed his predecessor, Abu Musab al-Zarqawi.
Since then, Iraqi officials have reported his death three times, his capture twice and a mortal wounding once.
This time, Nineveh Gov. Duraid Kashmoula and Iraqi Defense Ministry spokesman Gen. Mohammed al-Askari told CNN on Thursday that al-Muhajer had been captured during a late-night operation in Mosul, saying he had since been handed over to the U.S. military.
Kashmoula said that police, acting on very reliable sources, surrounded and stormed a house in Mosul's southern Wadi Hajer neighborhood, finding a man who readily identified himself as al-Muhajer sleeping on a thin mattress on the ground.
Iraqi security forces said they were 100 percent certain of the identification, he said. Al-Askari said he was captured in a joint U.S.-Iraqi operation in Mosul, although Kashmoula said no U.S. forces were involved.
Other Iraqi officials also reported al-Muhajer's capture. An aide to Interior Minister Jawad al-Bolani said he was captured by Iraqi police in Mosul and that the minister on Thursday evening called the Mosul police chief to praise their work.
An Interior Ministry spokesman, Maj. Gen. Abdul Karim Khalaf, told state-run TV about the capture, saying that "sources close to the criminal" led them to his hideout. Khalaf said "the criminal confessed to being al-Muhajer" following a preliminary interrogation and that further interrogations were under way.
The capture is "a major blow to al Qaeda in Iraq," he said.
Iraqi media reported the capture as breaking news and had several officials on air to talk about it.
But U.S. military officials could only say on the record they had nothing to confirm the report.
"I am seeing the same reports you are and am checking into it," Col. Steve Boylan told CNN on Thursday. "Have not heard any confirmation as yet. We are trying to get confirmation one way or the other."
""We do not have any operational reporting at this time that indicates that Abu Ayub al-Masri has been captured," another military spokesman said. "We are still checking with our Iraqi counterparts to verify the exact details."
And a senior federal law enforcement official told CNN that "U.S. intelligence officials have no information to confirm the report and at this point are skeptical of the reported capture."
The elusive al Qaeda in Iraq leader has been reported captured or killed before. In October 2006, just four months after he assumed al-Zarqawi's role as the group's leader, he was reported killed in a U.S. raid in Haditha. Seven months after that, he was supposedly killed in a clash between rival Sunni groups near Taji.
Neither report panned out. Neither did a report in February 2007 that he had been killed, then captured, then mortally wounded on the road between Samarra and Fallujah -- all in a two-day period.
Iraqi officials have also misreported the deaths or capture of other high-ranking insurgents, Baathists or others, including al-Zarqawi before he was finally killed and Izzat Ibrahim al-Douri, the highest-ranking former member of Saddam Hussein's regime still at large.
Al-Douri, who was the "King of Clubs" (No. 6) on the U.S. military's card deck of most wanted regime officials, was most recently reported captured two weeks ago by multiple Iraqi officials. He had previously been reported killed in 2005 and captured the year before.
CNN's Mohammed Tawfeeq, Jomana Karadsheh, Tommy Evans, Terry Frieden and Ingrid Formanek contributed to this report.