The interior ministry in
Abu Ayyub al-Masri has led the group since June 2006, when Abu Musab al-Zarqawi was killed in an air strike.
One official said he was "100% sure" Masri was dead, but another urged caution as they do not have the body.
An Iraqi resistance group denied Masri had been killed, in a statement posted on the internet.
The self-styled Islamic State in
"The Islamic State of Iraq reassures the Ummah [Muslim nation] on the safety of Sheikh Abu Hamza al-Muhajir, may God protect him, and that he is still fighting the enemies of God," the group said in a statement on a website commonly used by insurgents.
The Islamic State in
'Doubly sure'
Masri was "ambushed by rivals" on Tuesday in northern
"There were clashes within the groups of al-Qaeda. He was liquidated by them. Our forces had nothing to do with it," said interior ministry spokesman Brig Gen Abdel Karim Khalaf.
He said interior ministry sources had seen the killing.
But Iraqi government spokesman Ali al-Dabbagh cautioned: "This intelligence still has to be checked by giving the body to people who can identify him.
"When we get the body, its DNA must be verified, but the body is still not in the hands of Iraqi forces. There are now attempts by the Iraqi forces to get the body."
The
"I hope it's true, we're checking, but we're going to be doubly sure before we can confirm anything," said Lt Col Chris Garver.
He added that several previous reports of Masri's death had been unfounded. The
Masri is believed to have trained in
The group is blamed for or has claimed some of the bloodiest attacks in
The BBC's defense correspondent Rob Watson says if the reports are confirmed, this would be a highly significant development in terms of the manner of Masri's death.
Nevertheless, even if Masri is dead, it would be premature to expect a sudden drop in violence.
Al-Qaeda in
In other developments:
· At least 14 people were killed in two separate attacks on buses carrying passengers on a main road south of the capital,
· Mortar rounds hit the US-controlled Green Zone, with one striking within 100m (328 feet) of the Iraqi prime minister's offices, AP news agency quoted a government official as saying.
Photo caption
Abu Ayyub al-Masri
Source: BBC