Meanwhile, the U.S. military said eight U.S. soldiers and four American civilians died aboard a U.S. Army Black Hawk helicopter that crashed late Saturday in northern Iraq, according to the Associated Press.
Monday's attack is the latest in a string of insurgent assaults aimed at Iraqi police and also may have targeted officials attending the ceremonies.
At the time of the attacks, the U.S. ambassador and Iraq's interior and defense ministers were watching a parade of soldiers, police patrols and military equipment. U.S. Ambassador Zalmay Khalilzad was far from site of the bombing and therefore was not injured, a U.S. Embassy spokeswoman told the AP. Most of the dead were Iraqi policemen, according to the hospital.
The militant group known as Al-Qaida in Iraq claimed responsibility for the assault in a statement posted on a Web site generally used by insurgents.
Police shot and killed the first bomber at a checkpoint in the area, but his explosives still detonated, Police Maj. Falah al-Mohammadawi told the AP. A second bomber detonated his explosives shortly afterward.
Al-Qaida's statement described the bombers as brothers and said the first "got through nine check points" before detonating his explosives.
"After fear spread among the apostates, the second brother blew up his belt, bringing great misfortune upon them," the statement read, according to Reuters.
In other violence Monday, gunmen assassinated a judge in Kirkuk, and other attackers killed a doctor and an Iraqi intelligence officer near Baghdad.
The U.S. Army Black Hawk helicopter that went down Saturday was part of a two-helicopter team providing support for the 101st Airborne Division in northern Iraq.
The helicopter crashed as it traveled between bases in an area seven miles east of Tal Afar, near the Syrian border. It is an area that has seen heavy fighting with insurgents.
On Sunday, a car bomb killed two civilians west of Baqouba. And police found five bound and blindfolded bodies, apparently shot to death, in Baghdad, the AP reported.
Since Thursday, 28 Americans have died in Iraq and the death toll of U.S. service members killed in Iraq now stands at 2,207.
Meanwhile, debate continues over President Bush's plan to contain the insurgency by training Iraqis rather than increasing American troop levels.
On Sunday, Paul Bremer, the senior U.S. official in Iraq during the first year of the war, told NBC News that he had sent a memo to Defense Secretary Donald Rumsfeld in May 2004 suggesting that 500,000 troops were needed to contain the insurgency. The number was nearly three times the amount of troops stationed in the country at the time.
Pentagon officials confirmed Monday that Rumsfeld had received the request and rejected it.