The attack on the Zafraniyah neighborhood in southern Baghdad began about 7:15 p.m. with two car bombs and a barrage of an estimated nine rockets, Defense Ministry spokesman Col. Saddoun Abu al-Ula said.

He said the barrage heavily damaged three buildings, including a multistory apartment house that collapsed. Al-Ula said the rockets appeared to have been fired from Dora, one of the mostly Sunni districts targeted by U.S. troops in a new security crackdown against sectarian violence in the capital.

Police Lt. Thaer Mahmoud said 47 people were killed and 148 were wounded.

The complex style of the assault was similar to a July 27 attack of mortars, rockets and car bombs on another mostly Shiite district, Karradah, which killed 31 people. Police said the rockets and mortars that struck Karradah also were fired from Dora.

A Sunni extremist group, the al-Sahaba Soldiers, claimed responsibility for the Karradah attack to punish Shiites for supporting the "crusaders," or Americans, and the "treacherous" Iraqi government.

Muhanna Yassin, who lives in Zafraniyah, said the attack left the neighborhood "a total mess" with "bodies of the dead and injured scattered around in the streets - old, young, women and children."

"The ground shook underneath us and there was chaos everywhere," he said in a telephone interview. "Everyone was dazed and confused, looking for their families. Some children and grown-ups were crying. I can't even begin describing their state."

He said many of the victims were cut by flying glass and debris, leaving parts of the streets soaked in blood. Iraqi state television reported that some victims may be trapped in the rubble of the apartment building.

The multiple attacks were part of the grisly pattern of Sunni-Shiite violence that American officials consider the greatest threat to Iraq's stability more than three years after the U.S.-led invasion toppled Saddam Hussein's regime.

U.S. commanders are sending nearly 12,000 U.S. and Iraqi soldiers into the capital to curb the surge of sectarian violence, which was described by the U.S. ambassador to Iraq, Zalmay Khalilzad, on Sunday as "the principal problem here."

"I believe that the sectarian violence is serious. I believe the Iraqis have overcome challenges before ... and they can overcome this as well," Khalilzad said on CNN.

Earlier Sunday, the U.S. command announced that soldiers of the 2nd Brigade, 101st Airborne Division had arrested a key terrorist cell leader who was "directly linked" to the July 17 attack on an outdoor market in Mahmoudiya, about 20 miles south of Baghdad.

The statement said the arrest was made Thursday but did not give the suspect's name. Gunmen believed to be Sunnis opened fire on shoppers and vendors in the Mahmoudiya market during last month's attack, killing at least 51 people and wounding more than 70. Most of the victims were Shiites.

On Friday, U.S. soldiers arrested 60 Sunni men including members of an al-Qaida-affiliated cell that "specializes in bomb making" and carried out car bomb attacks in the capital, the U.S. command said.

Sectarian tensions have been rising following the Feb. 22 bombing at a Shiite shrine in Samarra, which triggered a wave of reprisal attacks against Sunni mosques and clerics. Tens of thousands of Iraqis have fled their homes since then, seeking refuge in areas where their Muslim sect is in the majority.

Much of the violence has been blamed on sectarian militias and armed groups that target members of the rival religious community. Prime Minister Nouri al-Maliki, a Shiite, has promised to disband the militias, some of which are linked to figures in his own government.

On Sunday, Health Minister Ali al-Shemari, a member of a Shiite group that operates a militia, said American soldiers arrested seven of his bodyguards in a pre-dawn raid on his office.

"There was no legal warrant, there was no prior warning to the ministry, there was no reason to arrest them. It is a provocation," said al-Shemari, a member of the movement led by radical Shiite cleric, Muqtada al-Sadr, head of the biggest Shiite militia, the Mahdi Army.

However, a U.S. military statement said coalition forces received a tip from a resident that "15 criminals wearing Iraqi army uniforms" had kidnapped six people and taken them to the Ministry of Health building.

Iraqi and U.S. soldiers searched the building and did not find any kidnap victims. But five detainees were taken in for questioning "based on their positive identification by the tipster," the statement said, without elaborating.

It was not clear if the raid was linked to the June disappearance of a Sunni provincial health official, Dr. Ali al-Mahdawi, who vanished after a meeting with the minister. Sunnis claimed al-Mahdawi was kidnapped by Shiite militiamen.

Al-Shemari denied any knowledge of al-Mahdawi's disappearance and said he had interviewed him for a senior post in the ministry.

Politicians from several factions, meanwhile, said Shiite and Kurdish parties are organizing a bid to oust the Sunni speaker of parliament.

Since taking office May 20, Mahmoud al-Mashhadani has made a number of statements that offended key constituencies, including speaking out against regional self-rule, strongly supported by Shiites and Kurds but opposed by many Sunni Arabs.

Al-Mashhadani's ouster, which could be done by a new vote in parliament, would be the first major shake-up in the government of national unity. Al-Mashhadani would likely be replaced by another Sunni Arab if the move against him succeeds.