BAGHDAD — Two bombs went off within minutes of each other in a packed Baghdad shopping district this evening, killing 42 people and wounding 120, the chief Iraqi military spokesman said.

There were no claims of responsibility, but double bombings became the hallmark of attacks on civilians by Al Qaeda in Iraq during the worst of the violence in Baghdad in 2006. An initial explosion was designed to draw in people, especially security and medical workers rushing to the scene, before a second larger bomb detonates to maximize casualties.

Today’s attack began when a roadside bomb exploded in the primarily Shiite, middle-class neighborhood of Karradah. A couple of minutes later, a bomb blew up in a nearby garbage can, the military spokesman, Brigadier General Qassim al-Moussawi, said.

Many of the victims were teenagers or young adults and four were women, police and hospital officials said.

A clothing store owner, Hassan Abdullah, was standing near his shop when the first explosion went off about 150 yards away. He started walking toward the scene when the second blast took place.

“I saw a leg and a hand falling near me as I was walking. The whole place was a mess,” Mr. Abdullah, 25, said. “Wounded people were crying for help and people started to run away. Police pickups and ambulances arrived at the scene to pick up the casualties.”

Mr. Abdullah said Karradah was crowded because it was the start of Iraq’s Friday-Saturday weekend and the weather was clear and pleasant.

“The aim of such attacks is the random killing of as many people as possible in order to terrorize the Iraqi people,” he said.

Violence has dropped substantially in Baghdad over the last half-year with the boost in American troops, a cease-fire by a powerful Shiite militia, and some Sunni fighters turning away from Al Qaeda in Iraq.