Blast Kills 8 at Iraqi Parliament Building

In November, a bomb exploded inside the Green Zone in an armored car that belonged to the speaker of parliament, wounding no one. About two weeks ago, two unexploded suicide vests were found inside the area. Before Thursday, the most serious breach of security inside the zone occurred in October 2004, when two bombs killed six people.

While the outer rings of security checks in the zone are run by guards contracted by the U.S. military, the parliament building hires its own guards, said Maj. Shawn Stroud, a U.S. military spokesman.

Thousands of politicians, U.S. government employees, civilian service workers and delivery people enter the Green Zone each day, showing various sorts of identification badges, some of which allow their holders to pass through without being searched.

"There are many people working in the building, and I do believe that we need to review our methods and procedures," said Brig. Gen. Qassim al-Mossawi, spokesman for the Baghdad security plan.

Earlier Thursday, a tank truck rigged with explosives was detonated on the Sarafiya bridge, collapsing a beloved landmark that was both a physical and a symbolic link between the capital's eastern and western sides.

The U.S. military said one person was killed and two were wounded in the blast. But Maj. Gen. Abdul Rasool al-Zaidi, director general of civil defense at the Interior Ministry, said the explosion killed two and wounded 11, and caused at least three cars to plunge into the Tigris.

Baghdad residents lamented the damage to the steel bridge, built by the British more than 50 years ago.

The blast woke Nasir Abdul Salam, 50, who ran outside to watch the rescue efforts. "Many old men were crying for this old pal that they lost," Salam said of the bridge. "It was almost their age."

Also Thursday, one U.S. soldier was killed in a shootout north of the capital, and a second soldier died of noncombat causes, the military said.

Reacting to the Green Zone attack, the White House emphasized its commitment to the U.S. effort in Iraq. Bush, who faces growing congressional pressure for a time frame to begin a withdrawal, said his message to Iraq was that Americans "stand with you" as the Shiite-led government of Prime Minister Nouri al-Maliki tries to achieve national reconciliation and fight an increasingly complex variety of insurgents, militias and Islamic extremists.

"This assembly is a place where people have come to represent the 12 million people who voted," the president said, referring to the parliament building. "There's a type of person that would walk in that building and kill innocent life, and that is the same type of person that is willing to come and kill innocent Americans."

Rice, national security adviser Stephen J. Hadley and others talked to the new U.S. ambassador to Iraq, Ryan C. Crocker, throughout the day, an unusual degree of engagement by the highest levels of the U.S. government.