Azzam was shot by U.S. and Iraqi forces in a raid on a Baghdad apartment building. The plan was to capture Azzam alive, but he was killed in a shootout.
U.S. military officials said Azzam had been tracked for some time, and the raid on the apartment came after a specific tip-off.
Laith Kubba, a spokesman for the Iraqi prime minister's office told journalists that Azzam had been behind many terror attacks.
"It was discovered that the man who was killed is Abdallah Najim Abdallah Al-Juwari, an Iraqi, also known as Abu Azzam, who is the number one for Al-Qaeda in Baghdad and the second-in-command in Iraq. This is important news because Abu Azzam is responsible for carrying out indiscriminate attacks in Baghdad, especially against the Shi'ites," Kubba said.
Myers, at a press conference outside Washington confirmed that Azzam had been a "big fish," particularly concerning insurgent operations in the Iraqi capital Baghdad.
"Now, the number two person, the person that is [al-Zarqawi's] primary facilitator, the one that organizes things operationally, certainly in Baghdad, and has a lot of responsibility for the Al-Qaeda finances in Iraq, he is no longer on the scene," Myers said.
Al-Qaeda however sought to play down the significance of the action. A statement posted on a website described Azzam as only head of "one of Al-Qaeda's units" in Baghdad, and described as "lies" the assertion that he was second-in-command to Zarqawi. The statement even cast doubt on whether he was really dead.
Myers conceded that the loss of Azzam will probably not be a fatal blow to Al-Qaeda in Iraq, and that the terror group will find a replacement. But he was the latest and most important of several of al-Zarqawi's associates to be killed or captured, and Myers said that "clearly, al-Zarqawi knows that he is under a lot of pressure."
Nevertheless, the elusive Jordanian-born al-Zarqawi has managed to escape so far, despite the bounty of $25 million on his head. He is thought to be hiding in the Euphrates Valley of western Iraq.
Al-Zarqawi has emerged as the key figure in the Iraqi insurgency, and his group has claimed responsibilty for spectacular insurgent attacks in Iraq, including scores of car bombings, along with multiple kidnappings and beheadings.
An extremist Sunni Muslim, al-Zarqawi has recently pledged all-out war on Iraq's majority Shi'ites, who dominate Iraq’s U.S.-backed interim government.
In his remarks to reporters, General Myers said the insurgency will be defeated in Iraq, but that it will take time.
"We will be victorious, and will help [the Iraqis] with victory in Iraq, but Iraq will be perhaps a longer-term issue, it's an insurgency which must be dealt with over a longer period of time, in which the political and economic levers of power are going to play a major, major role," Myers said.
General Myers is about to retire, and he won praise at the press conference for his efforts in Iraq from Defense Secretary Donald Rumsfeld.