BAGHDAD, Iraq — A bomb tore through food stalls and kiosks in a sprawling Shiite slum today, killing at least 33 people, while the U.S. military announced the death of the 100th servicemember in Iraq this month.

The 6:15 a.m. explosion in Sadr City targeted poor Shiites who gather there each morning hoping to be hired as construction workers. At least 59 people were wounded, said police Maj. Hashim al-Yasiri.

The area of today's attack, a stronghold of the Mahdi Army militia loyal to radical Shiite cleric Muqtada al-Sadr, has witnessed repeated bombings by suspected al-Qaida fighters seeking to incite Shiite revenge attacks and drag the country into full-blown civil war.

Ali Abdul-Ridha, being treated for head and shoulder wounds at a hospital, said he was waiting for a job with his brother and about 100 others when he heard a massive explosion and "lost sight of everything."

The U.S. and Iraqi military have kept a tight cordon around Sadr City since a raid last week in search of an alleged Shiite death squad leader, who was not found.

Abdul-Ridha said the area had been exposed to attack because U.S. and Iraqi forces had driven Mahdi fighters who usually provide protection into hiding.

"That forced Mahdi Army members, who were patrolling the streets, to vanish," Abdul-Ridha, 41, said from his bed in al-Sadr Hospital.

However, Falih Jabar, a 37-year-old father of two boys, said the Mahdi Army was responsible for provoking extremists to attack civilians in the neighborhood of 2.5 million people.

"We are poor people just looking to make a living. We have nothing to do with any conflict," said Jabar, who suffered back wounds. "If (the extremists) have problems with the Mahdi Army, they must fight them, not us."

The 33 victims in Sadr City were part of an overall toll of 78 people killed or found dead in Iraq today.

The U.S. military identified its latest casualty as a Marine assigned to Regimental Combat Team 5 who died in combat Sunday in Anbar province west of Baghdad, a hotbed of Sunni resistance to U.S. forces and their Iraqi government allies.

Since a brief lull during Muslim holy days last week, violence has rebounded sharply, marring U.S. efforts to bring Sunni insurgents into a reconciliation process.

Meanwhile, new details emerged about a U.S. soldier who disappeared last week, sparking a massive manhunt. A woman claiming to be his mother-in-law said today that the soldier was married to a Baghdad college student and was with the young woman and her family when hooded gunmen handcuffed and threw him in the back seat of a white Mercedes. The marriage would violate military regulations.

The Iraqi woman said several of the soldier's in-laws put up a desperate struggle to stop the abduction.

The U.S. military has said the soldier was of Iraqi descent and that he was visiting family in the central Baghdad neighborhood of Karadah when he was abducted. It did not identify the soldier or give further details. The soldier's in-laws said his name is Ahmed Qusai al-Taayie.