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.

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 Monday 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.

U.S. National Security Adviser Stephen Hadley made an unannounced visit to Baghdad, where he met with his Iraqi counterpart, Mouwafak al-Rubaie, for talks on military and political coordination, the government said.

A commission to coordinate U.S.-Iraqi relations, especially military activity, was established in a video conference Saturday between President Bush and Prime Minister Nouri al-Maliki, who has issued critical statements about U.S. policy in the past week.

“The two sides discussed the work of the committee which agreed to by between the prime minister and the American president and is designed to coordinate development of the Iraqi security forces, expedite military training, reconciliation among Iraqis and the war against terrorism,” the statement said.

Gordon Johndroe, spokesman for the National Security Council, said Hadley's visit was not a fence-mending effort to deal with strains between Washington and Baghdad. “Absolutely not,” Johndroe said. “This is a long planned trip to get a first hand report of the situation on the ground from the political, economic and security fronts.”

The area of today's attack, a stronghold of the Mahdi Army militia loyal to radical Shiite cleric Muqtada al-Sadr, has seen repeated bombings by suspected al-Qaida fighters seeking to incite Shiite revenge attacks and drag Iraq into a 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 last major bombing in Sadr City occurred Sept. 23 when a bomb blew up a kerosene tanker, killing 35 people waiting to stock up on fuel for the Muslim holy month of Ramadan.

The 33 victims in Sadr City were part of an overall toll of 80 people killed or found dead in Iraq today.

October has seen rising civilian casualties and has been the fourth deadliest month for U.S. troops since the war began in March 2003. The highest was November 2004, with 137 killed, followed by 135 in April 2004 and 107 in January 2005.

The U.S. military identified the latest casualty as a Marine assigned to Regimental Combat Team 5 who died in combat Sunday in Anbar province, a hotbed of resistance.

In Baghdad, the Iraqi woman claiming to be the missing soldier's mother-in-law said several of his 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 Qais al-Taayie.

The woman, who identified herself as Latifah Isfieh Nasser, told The Associated Press in the family home in Karadah that her daughter, 26-year-old physics student Israa Abdul-Satar, met her husband a year ago and the couple were married in August and honeymooned in Egypt. She showed an AP reporter photographs of the couple in Cairo.

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.

Political tensions deepened further Sunday when Vice President Tariq al-Hashemi, the country's ranking Sunni politician, threatened to resign if al-Maliki did not move swiftly to eradicate militia groups.

Mohammed Shaker, a key aide to al-Hashemi, said the threat was intended to send a message to the government over the rising sectarian violence. “We cannot live with this situation indefinitely,” he said.

He was joined today by a Sunni ally, Adnan al-Dulaimi, who threatened to withdraw the Iraqi Accordance Front from parliament and the Cabinet unless security improved.

“If current conditions continue, Iraq will be destroyed,” al-Dulaimi said.

Al-Maliki depends heavily on the backing of a pair of Shiite political organizations and has resisted U.S. pressure to eradicate their private armies - al-Sadr's Mahdi Army and the Badr Brigade, the military wing of Iraq's most powerful Shiite political bloc, the Supreme Council for the Islamic Revolution in Iraq.

The gunmen, especially those of the Mahdi Army, have been deeply involved in months of sectarian killings in Baghdad and central Iraq.

The militias have also infiltrated the predominantly Shiite security forces, who suffered around 300 deaths during Ramadan, mainly at the hands of Sunni insurgents but also in fighting between police and militia fighters.

At least 26 policemen were killed Sunday.

In one attack in Basra, gunmen dragged 15 policemen and two translators - instructors at the Basra police academy - off a bus at the edge of the city. Their bodies were found hours later.

Three other policemen were killed when a car bomb hit a patrol Sunday night in northeastern Baghdad's Bunook neighborhood, police Lt. Ahmed Mohammed Ali said.

Today, unknown gunmen killed Essam al-Rawi, head of the University Professor's Union and a senior member of the hard-line Sunni group, the Association of Muslim Scholars. One of his bodyguards was also killed.

The association, which is believed to have links to the insurgency, has boycotted elections and other aspects of the political process that seeks to bring stability and end rampant sectarian violence.

At least 154 university professors have been killed since the March 2003 U.S. invasion, Education Ministry spokesman Basil al-Khatib said. Hundreds, possibly thousands, more are believed to have fled to neighboring countries.

While sectarian hatred is blamed for some of those attacks, professors have also been killed because of past membership in Saddam Hussein's now-outlawed Baath Party, or by students angered over poor grades or with other grievances.