U.S. troops complied with orders from Prime Minister Nouri al-Maliki Tuesday to abandon checkpoints around Baghdad, including ones in and around the Shiite militia stronghold of Sadr City.

Soon after U.S. forces began removing concrete blocks and sandbags from security checkpoints, a homicide car bomber targeted a wedding ceremony in the capital, killing 11 people, including four children, police said.

The bomber plowed a car packed with explosives into a crowd of Shiite celebrants preparing to board vehicles outside the bride's home in the Shaab neighborhood of Baghdad, Lt. Ahmed Mohamed of the Risafa police station said.

Baghdad police earlier reported the deaths of three people in a car bomb explosion and the discovery of five bodies, including one woman.

U.S. officials said they did not receive advance warning of the order to remove the barriers by 5 p.m. local time Tuesday. Military spokesman, Lt. Col. Christopher Garver, said officers were meeting to "formulate a response to address the prime minister's concerns."

The tightened security had been credited by some for producing a temporary decline in violence, possibly because they curbed the activities of Shiite death squads blamed for waves of sectarian killings of Sunnis.

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The extra checkpoints were set up last week around Sadr City as U.S. troops launched an intensive search for a missing American soldier and raided homes looking for death squad leaders in the sprawling slum that is home to an overwhelmingly Shiite population of 2.5 million people.

Other checkpoints manned by U.S. troops were erected in the downtown Karradah neighborhood where the soldier had been abducted.

Al-Maliki's statement said such measures "should not be taken except during nighttime curfew hours and emergencies."

"Joint efforts continue to pursue terrorists and outlaws who expose the lives of citizens to killings, abductions and explosions," said the statement, issued in al-Maliki's name in his capacity both as prime minister and commander of the Iraqi armed forces.

Earlier in the day, Shiite gunmen largely shut down access to Sadr City to demand the removal of the checkpoints, acting on orders from radical anti-American cleric Muqtada al-Sadr.

In a statement addressed to local supporters on Monday, al-Sadr warned of unspecified action if the military's "siege" continues. He also criticized what he called the silence of politicians over actions by the U.S. military in the district on Baghdad's northeastern edge.

"If this siege continues for long, we will resort to actions which I will have no choice but to take, God willing, and when the time is right," he said in the statement.

Al-Maliki's demand threatened to further upset relations between the U.S. and the Iraqi government, which hit a rough patch last week after Al-Maliki issued a string of bitter complaints, at one point saying he was not "America's man in Iraq."

Al-Maliki was apparently angered by a statement from U.S. Ambassador Zalmay Khalilzad that the prime minister had agreed to set a timeline for progress on reaching security and political goals — something al-Maliki denied.

U.S. concern over the deteriorating relationship was evident when National Security Adviser Stephen Hadley showed up unannounced in Baghdad on Monday to meet with al-Maliki and his security chief, Mouwafak al-Rubaie.

Al-Rubaie told The Associated Press late Monday that Hadley was in Iraq to discuss the work of a five-person committee that al-Maliki and Bush had agreed to Saturday. Hadley also presented some proposals concerning the training and equipping of Iraqi security forces, as well as security plans. U.S. spokesmen could not immediately be reached on Tuesday and it wasn't known whether Hadley had returned to Washington.

American voter support for the war is at a low point as the Nov. 7 midterm elections approach, and a top aide to al-Maliki said the Iraqi leader was using the Republicans' vulnerability on the issue to leverage concessions from the Bush administration — particularly the speedy withdrawal of American forces from Iraqi cities to U.S. bases in the country.

Al-Maliki has said he believes that the continued presence of American forces in Iraq's population centers is partly behind the surge in violence.

Meanwhile, the U.S. military announced the deaths of two soldiers in fighting Monday, bringing the number of troops killed in Iraq this month to 103.

October has been the fourth deadliest month for American troops since the war began in March 2003. The other highest monthly death tolls were 107 in January 2005; at least 135 in April 2004, and 137 in November 2004.

The military had no immediate comment on a CBS News report saying the top U.S. commander in Iraq, Gen. George Casey was expected to recommend Iraq's ill-equipped and marginally effective security forces be increased by up to 100,000 troops. Casey said last month that he wouldn't rule out asking for more forces, something that could allow U.S. troop levels to be gradually reduced.

At least three Iraqi policemen were also reported killed on Tuesday morning in Baghdad and the volatile western city of Falujah, police said.

Sheik Raed Naeem al-Juheishi, the head of a non-governmental organization dedicated to tracing the fate of victims of the former regime of Saddam Hussein, was also killed in a drive-by-shooting Monday night in Baghdad's chaotic Dora district, Col. Mohammed Ali said.

New violence that followed a lull during last week's Muslim holy days claimed the lives of at least 81 people across Iraq on Monday.

According to an Associated Press count, October has recorded more Iraqi civilian deaths — 1,170 as of Monday — than any other month since the AP began keeping track in May 2005. The next-highest month was March 2006, when 1,038 Iraqi civilians were killed in the aftermath of the Feb. 22 bombing of an important Shiite shrine in Samarra.

The Associated Press contributed to this report.