A car bomb ripped through a busy commercial street in a Shiite area of Baghdad, killing at least 51 people Tuesday and wounding scores more in the deadliest blast in the capital in more than three months.

Many of the victims were trapped in their apartments by a raging fire that engulfed at least one building, according to police and Interior Ministry officials who said about 75 people were wounded.

The blast shattered the relative calm which has prevailed in the capital since a cease-fire on May 11 brought an end to seven weeks of fighting between U.S. and Iraqi forces and Shiite militants in the Sadr City district of Baghdad.

It occurred about 5:45 p.m. near a market and bus stop in the Hurriyah district of west Baghdad, scene of some of the most horrific sectarian massacres during the wave of Sunni-Shiite slaughter in 2006.

The blast was the deadliest attack in Baghdad since March 6, when a pair of bombs detonated within minutes in the mostly Shiite district of Karradah, killing 68 people and wounding about 120.

Kamil Jassim said the blast set fire to a generator used by local residents and shopkeepers to supplement city power. The fire quickly spread to a two-story building containing both shops and apartments where many of the victims were found.

Stunned survivors stumbled through the rubble-strewn street which was filled with the smoke from burning vehicles, witnesses said.

Anguished families jammed nearby hospitals, weeping for their dead and injured loved ones. Angry survivors blamed the army and police for failing to protect them.

"The blast occurred because there wasn't any security presence by the Iraqi army or police at the scene, not even any checkpoint," said Khalid Hassan, 40, who suffered shrapnel wounds and burns. "People were confused, upset and running in all directions. We are all victims of terrorism and carelessness."

Haider Fadhil, a 25-year-old metal worker, said he was shopping with two friends when the blast hurled him to the ground.

"When I regained consciousness, I found that my left hand and leg were broken," Fadhil said from his hospital bed. "Thanks be to God for saving me and thanks to those who carried me in their pickup truck to the hospital."

No group claimed responsibility for the blast, and both Sunni and Shiite militants have used car bombs in their attacks.

"This is a senseless and tragic event," said Lt. Col. Steve Stover, a spokesman for the U.S. military's Baghdad command. "What's to gain by terrorizing the population? ... This is simply an evil act."

U.S. commanders have warned repeatedly that the relative peace which has prevailed in Baghdad is fragile because extremists, including Al Qaeda in Iraq and Shiite militant groups, remain capable of high-profile attacks.

The Americans hope that security measures are enough to prevent extremists from mounting a sustained campaign of bombings against civilians that could provoke a return to sectarian reprisal attacks.

Despite the uncertainty, Iraqi officials have been anxious to promote a sense of confidence among the war-weary Iraqi people after months of declining bloodshed in the capital.

Deputy parliamentary speaker Khalid al-Attiyah told lawmakers Tuesday that they will move from the convention center in the Green Zone to the Saddam Hussein-era National Assembly building for their next legislative term, which begins Sept. 1.

The move could help parliament affirm its independence from the Americans and shed its public image as an institution isolated from the people since the U.S.-protected enclave.

"There is progress in the security situation and the reconstruction has been completed of the new building," al-Attiyah said, adding the new accommodations will be large enough for the full 275-member legislature and staff members.

The National Assembly building was used by the Iraqi parliament under Saddam and is located in the Allawi district, a religiously mixed area about 500 yards from the blast walls that form the perimeter of the Green Zone on the west side of the Tigris River.

It was looted and burned during the chaos that followed the fall of Baghdad to U.S. forces in April 2003. But al-Attiyah said its reconstruction has been completed.

Also Tuesday, an Iraqi state television journalist, Muhieddin Abdul-Hamid, was shot to death near his apartment in the northern city of Mosul, officials said.

Colleagues said the 50-year-old journalist was a local anchor for the TV station in Mosul, the focus of an ongoing U.S.-Iraqi operation against the last major urban stronghold of Al Qaeda in Iraq.

Excluding Abdul-Hamid, the New York-based Committee to Protect Journalists says at least 129 journalists and 50 media support workers have been killed since the U.S. invasion in 2003.

In other violence Tuesday, a homicide bomber on a motorcycle struck a Baghdad checkpoint manned by U.S.-allied fighters, killing one and wounding four, officials said.

Another homicide car bomber struck a police checkpoint in downtown Baqouba, northeast of Baghdad, killing one policeman and wounding 19 other people, officials said.

Gunmen also killed a senior police officer and two of his guards near Aziziyah, a Shiite area 35 miles southeast of Baghdad.

South of Baghdad, Iraq's Interior Ministry spokesman Maj. Gen. Abdul-Karim Khalaf said in Amarah that large numbers of gunmen have surrendered to government forces and handed over weapons ahead of a military operation due to begin there on Thursday. He was not more specific.

The Iraqi government has given residents in Amarah a Wednesday deadline to turn over heavy weapons, saying it hoped to "demilitarize" the Shiite city without bloodshed.

Iraqi troops have fanned out across Amarah, a stronghold of anti-U.S. cleric Muqtada al-Sadr's Mahdi Army militia and the purported center of weapons smuggling from Iran.

But no fighting has been reported and Sadrist officials have said they won't put up any resistance unless government troops make arrests without warrants or commit other violations.