From the New York Times:

BAGHDAD, Dec. 12 — At least 56 people, most of them laborers looking for work, were killed today when a pickup truck packed with explosives was detonated in a crowded square in the city’s center this morning, Iraqi officials and witnesses said. At least 220 more were wounded.
...
American military officials have described the battle for control of Baghdad as a steady stream of individual killings of Sunnis carried out by Shiite death squads, punctuated by bombings and larger attacks carried out by Sunni insurgents or Al Qaeda members against Shiites
....
The speaker of the Iraqi Parliament, Mahmud Mashhadani, a Sunni, also denounced the attack, saying it was the work of “outlaws and those without a religion.”

Riiiiiight. This sure sounds like the work of the Iraqi Militant Atheists' Brigade. We just need to teach the bombers to be more passionate Muslims and this will all be solved.