Al-Qaeda's second-in-command in Iraq has been shot dead in a raid in Baghdad, US and Iraqi officials say.
Abu Azzam was said to be in charge of operations in Baghdad
Abu Azzam is described as the top aide to Abu Musab al-Zarqawi.
Iraqi Prime Minister Ibrahim al-Jaafari called the killing very important, and said those who informed on insurgents were helping to save hundreds of lives.
However, a statement purportedly from al-Qaeda in Iraq says it cannot confirm the death, and denies Azzam is the group's number two in the country.
In a separate incident, at least 10 people died in an attack on police recruits north of Baghdad.
At least 26 people were injured in the suicide blast in Baquba - the third major attack on Iraqi police in the last three days.
In other developments:
- The bodies of 22 men, blindfolded and shot, are found in the countryside near the Iranian border
- Gunmen fire on a police convoy taking detainees to Abu Ghraib jail, killing two people and wounding at least eight
- Five civilians are injured as a car bomb explodes in central Baghdad
- A police officer dies in a bomb attack in Kirkuk
Iraqi national security chief Mowaffak al-Rubaie praised the operation against Azzam.
"We are pretty sure that we have got the number two in al-Qaeda, in Iraq, the one who's after Zarqawi, and to be quite honest with you, we're quite happy with the outcome," he told the BBC.
ABU AZZAM PROFILE
Real name reported to be Abdallah Muhammed al-Juhaari
Also known as Sheikh Abdullah Abu Azzam, or the Emir of Anbar
Based in Baghdad since April
Financier and aide to Abu Musab al-Zarqawi, oversaw bombing campaign in the capital
Believed to be Palestinian
$50,000 reward for his death or capture
A US military official said Azzam was killed in a high-rise block in the Iraqi capital after a tip-off from an Iraqi citizen.
"During the operation, which was held with the intent of capturing him, he fired and he was killed by return fire," Maj Flora Lee said.
But US and Iraq officials differed over the timing of the raid.
Maj Lee said it happened at 0450 local time on Sunday, while Iraq officials said it happened on Monday.
Another US spokesman said Azzam had been tracked for some time, and his death was a "significant development".
"This shows that we are actively going after the network. We've taken down the number two in the network and that is going to have an impact," Lt Col Steve Boylan said.
"And whoever replaces him as number two, we will go after him as well."
BBC world affairs correspondent Nick Childs says that while the killing could be an important public relations boost for the US, it is not clear how significant Azzam is or whether his death could have a lasting impact.
The US authorities are offering $25m for the capture of Zarqawi, who is believed to be behind the beheadings of several foreigners, as well as a long list of suicide bombings and other attacks.
Tuesday's attack took place at 1000 local time (0600 GMT) at a centre for recruiting the elite Rapid Reaction Force, in Baquba's al-Jadida district.
A US military spokesman said the bomber approached the police station on foot, making no attempt to conceal his suicide belt.
The victims are thought to include serving police, people queuing for recruitment and passers-by.