The Islamic State of Iraq, an insurgent umbrella group which includes Al Qaeda in Iraq, claimed Friday one of its "knights" carried out the parliament suicide bombing in Baghdad's Green Zone, and the U.S. military revised the death toll sharply downward to one dead.

The Islamic State said in an Internet posting that it had delayed issuing the claim of responsibility to allow its men time to flee.

Iraqi officials, who spoke on condition of anonymity because the investigation was incomplete, said the bomber was believed to have been a bodyguard for an unnamed Sunni lawmaker who was not among the casualties.

"A knight from the state of Islam ... reached the heart of the Green Zone ... the temporary headquarters of the mice of the infidel parliament and blew himself up among a gathering of the infidel masters," the Islamic State said in the statement posted on one Islamist Web site commonly used by insurgents.

The Site Institute, which tracks militant web postings, said the claim by the Islamic State was authentic.

In a statement Friday morning, the U.S. military said "after further research and consultation with government of Iraq officials" it had determined that only one "civilian" had been killed in the attack and 22 were wounded.

Parliament officials said the victim was Mohammed Awad, a Sunni member of the moderate National Dialogue Front. Seven of the wounded were members of parliament, the officials said.

U.S. military spokesmanMaj. Gen. William Caldwell had said Thursday that eight people were killed in the bombing, a major security breach in the most heavily guard region of Baghdad.

Iraqi lawmakers, meanwhile, expressed outrage and resolve Friday in a rare session of parliament on the Muslim day of prayer. A red and white bouquet sat Awad's place in the parliament chamber.

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Lawmakers took the podium one after another to denounce the bombing. One MP had his arm in sling and a woman lawmaker wore a neck brace.

"The more they (terrorists) act, the more solid we become. When they take from us one martyr, we will offer more martyrs," Vice President Adil Abdul-Mahdi said. "The more they target our unity, the stronger our unity becomes."

But the turnout was low because of a weekly Friday ban on driving.

"Very few parliament members showed up because of the curfew," said Mohammed Abu Bakr, head of the parliament's media office. "Also the MPs' turnout is very low today because most of them are visiting those who were wounded by the blast," he said.

Some additional members filed into the parliament room and took their seats after the session was under way, but the room remained less than half full. The meeting began late, and adjourned after about 90 minutes.

The parliament chamber bore no signs of damage, but cleanup had yet to begin elsewhere in the building, where investigators were still combing through the debris for clues as to who was behind the attack and how they penetrated the tightest security in Baghdad — the heavily fortified Green Zone compound, which houses the U.S. Embassy as well as offices of the Iraqi government.

"The cafeteria is still not clean. There is still flesh of the bomber on the floor," Abu Bakr said. "Broken glass has not been removed, and a meeting hall is still full of dust."

Iraqi parliament speaker Mahmoud al-Mashhadani opened Friday's session by asking members of recite verses from the Quran to mourn Awad, who he called a "hero."

The meeting was "a clear message to all the terrorists and all those who dare try to stop this (political) process, that we will sacrifice in order for it to continue," al-Mashhadani said.

"We feel today that we are stronger that yesterday," he said. "The parliament, government and the people are all the same — they are all in the same ship which, if it sinks, will make everyone sink."

Deputy Prime Minister Barham Saleh told lawmakers that the government "had received indications that this building would be targeted." Before the attack Thursday, security guards took the unusual precaution of using sniffer dogs to search inside the parliament building.

State-run Iraqiya television's transmission was draped Friday in a black mourning banner. Regular programming aired, but the screen had a black stripe across the upper left hand corner.

Several TV channels replayed images Friday of the moment of the attack and the minutes following: a flash and an orange ball of fire causing Jalaluddin al-Saghir, a startled parliament member who was being interviewed, to duck. Smoke and dust billowed through the area, and confused and frightened lawmakers and others could be heard screaming for help. Al-Saghir escaped injury.

But a woman was shown kneeling over what appeared to be a wounded or dead man near a table and chairs. The camera then focused on a bloody, severed leg — apparently that of the suicide bomber.

The stunning breach of security at parliament — along with another bombing the same day that destroyed a bridge across the Tigris river and killed at least 11 people — struck a blow to a two-month-old U.S.-Iraqi effort to pacify the capital. Violence was down slightly in Baghdad, but the crackdown was insufficient to halt Thursday's spectacular attacks.

Nassar al-Rubaie, head of the parliamentary bloc allied with radical Shiite cleric Muqtada al-Sadr, accused the U.S. of lax security that allowed the bomber in.

"The occupation forces are in charge of security of this area. But no one dares to hold them responsible for this issue," he said.

"The problem of the occupation is not inside or outside this hall, it is for all Iraqi people. Why don't we hold them completely responsible?"

Caldwell said the attack bore the trademarks of al-Qaida in Iraq.

"We don't know at this point who it was. We do know in the past that suicide vests have been used predominantly by al-Qaida," he said.

U.S. forces captured 14 suspected al-Qaida in Iraq members in raids early Friday, the military said in a statement.

On Friday, police said 11 civilians had been killed in the bridge bombing a day earlier. Seven were killed in the explosion by a powerful suicide truck bomb, and four perished when their cars plummeted into the river below, police said. At least 39 people were injured, including three Iraqi soldiers. Two civilians are still missing, they said.

A roadside bomb killed one policeman and wounded four others in southern Baghdad on Friday, police said. A civilian was also wounded.

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