AMARAH, Iraq - Three coordinated car bombs ripped through the main street of this southern city yesterday, killing at least 42 people and wounding at least 125 in the largest bombing in Iraq since August.

The police chief of Amarah, a predominantly Shiite Muslim city that had never been struck by a car bomb before, was immediately fired for negligence.

"Amarah has never seen such an explosion before," said Abdel Karim Khalaf, chief spokesman for Iraq's Interior Ministry, who was dispatched to the city from Baghdad, 200 miles to the northwest. "A triple explosion surely indicates that the security forces have been infiltrated."

Southern Iraq, with its overwhelmingly Shiite population, largely has been free of the kind of sectarian violence that has wracked Baghdad and other mixed areas as Sunni Muslims and Shiites have fought for turf.

But the region has seen increased fighting - including assassinations of political figures and police officials - as two Shiite factions, the Mahdi Army of cleric Muqtada al-Sadr and the Badr Organization, the armed wing of the Islamic Supreme Council of Iraq, battle for control.

The two groups faced off in Amarah in October 2006, when 800 members of the Mahdi Army seized the town, which the Badr Organization had controlled. That siege lasted a day, until Iraqi government forces entered the city. Amarah had been peaceful since then.

In Baghdad, a car bomb killed at least five people and injured 13 yesterday.

Who might be behind the blasts in Amarah, which devastated restaurants and shops in the oil-rich city's center, was uncertain.

No group claimed responsibility, and the explosions appeared to be from bomb-rigged cars rather than suicide attacks.

Car bombs in other parts of Iraq, including Baghdad, usually are attributed to the Sunni extremist group al-Qaeda in Iraq, which has only a small presence in the south, and often involve suicide attackers.

Fears are rising about whether Iraq's mostly Shiite national security forces can control the Shiite militias competing for power in the oil-producing south.

U.S. commanders fear that al-Qaeda in Iraq and other extremists might try to exploit the security gap by attempting devastating attacks against Shiite civilians in less-protected areas outside Baghdad - especially where there is little coalition military presence.

The blasts in Amarah occurred only days before British forces are expected to hand over to local control a neighboring southern province - the last remaining under British control since the 2003 invasion.

Witnesses to yesterday's explosions said the first went off about 10:30 a.m.

Kareem al-Hmaidawi, 48, felt the explosion in his home and ran to the door, readying himself to try to help. His wife stopped him and they argued. She begged him to stay, and a second explosion shook their home.

"I could hear the weeping and the noise," Hmaidawi said. Finally, his wife let him go, and as he walked out he heard a third blast. He said tens of bodies lay on the road as he ran to help.

At the al Sadr General Hospital, dozens of women filled the hallways, crying for their loved ones as doctors and hospital workers tried to shoo them out. The injured filled the beds, and people flowed in to give blood.

Sunni Vice President Tariq al-Hashemi and Shiite Prime Minister Nouri al-Maliki condemned the attacks. Maliki called them a "desperate attempt to attract attention away from the clear successes" the government has had in cutting violence elsewhere.

Defense-Policy Bill Passes the House

The House passed

a defense- policy bill yesterday that would authorize $696 billion in military programs, including $189 billion for the wars in Iraq and Afghanistan.

The measure,

which covers the budget year that began Oct. 1, does not send money to the Pentagon. But it is considered a crucial policy measure because it guides companion spending legislation.

The Senate intends

to follow suit and send the bill to President Bush, who is expected to sign it. The House vote was 370-49. All area representatives voted for the bill except Rep. Chaka Fattah (D., Pa.).

The legislation includes

a 3.5 percent pay raise for uniformed service personnel and a guarantee that combat veterans receive swift health evaluations.

It also includes several

provisions intended to increase the oversight of contractors

- Associated Press

This article contains information from the Associated Press.