The parliament's 275 members, elected during Jan. 30 elections, convened in an auditorium amid tight security in the heavily guarded Green Zone with U.S. helicopter gunships hovering overhead.
Minutes before convening, at least a half dozen explosions detonated a few hundred yards away. The U.S. military said two mortar rounds landed inside the zone but caused no injuries.
The lawmakers opened with a reading of verses from the Quran. Iraqi Chief Justice Medhat al Mahmoud then administered the oath to the assembled deputies.
"It is a great day in Iraqi history that its elected representatives meet," said Fuad Masoum, a Kurdish delegate. "This day coincides with a painful memory that has many meanings. ... Today, on this occasion, we celebrate the inauguration of parliament after the fall of this regime."
Wednesday marked the anniversary of the Saddam Hussein-ordered chemical attack in 1988 on the northern Kurdish town of Halabja, an attack that killed 5,000 people.
In other developments:
Iraqi leaders have not yet agreed on a coalition government, and the leader of the Shiite-dominated United Iraqi Alliance, cleric Abdel Aziz al-Hakim, said his alliance hoped to "form a government whose motto is to serve the Iraqi people, a government of national unity and reconciliation."
"A government that can root out violence and set a trial for Saddam and the elements of his regime," Hakim said in a speech that wove in and out of prayer. He said a government led by the alliance would also try "to achieve the independence of Iraq and put an end to the role of multinational forces in Iraq."
Jalal Talabani, the Kurdish leader who will probably become Iraq's next president, said deputies "all have a duty to achieve real national unity."
"Iraq is facing tough times due to the continuation of criminal terror crimes," he said. "Al Qaeda is waging a war of extermination on Kurds and Shiites."
The alliance and a Kurdish coalition agreed last week to form a coalition government with Shiite politician Ibrahim al-Jaafari as prime minister. In return, Talabani will become Iraq's first Kurdish president, though the presidency is a largely ceremonial post.
To prevent suicide car bomb attacks against Iraq's new lawmakers, authorities stepped up security around the heavily fortified Green Zone. Two bridges leading to the zone were shut down Tuesday, and roadblocks were erected on other streets leading to the area.
On Tuesday, Shiite Muslim officials said they failed to reach final agreement in talks with the Kurds — who are mostly Sunni Muslim but secular — and the Sunni Arabs.
Ali al-Dabagh, a member of the Shiite clergy-dominated United Iraqi Alliance, which won the most seats in the elections, said Tuesday that Shiite, Kurdish and Sunni Arab politicians would meet after the deputies are sworn in "to finalize things. We need two to three days to announce an agreement."
The Shiite alliance won 140 seats in the National Assembly but needs the Kurds' 75 seats to assemble the two-thirds majority required to elect a president, who will then nominate the prime minister.
Shiite talks with Sunni Arabs focused on naming a parliament speaker, and it remained unclear if they would present a candidate Wednesday. Although the speaker's role is mostly restricted to presiding over the assembly and moderating discussions, the job has a great deal of visibility.
Sunni Arabs are believed to make up the core of the insurgency, and including them in the political process is seen as a way to isolate the militants.
"The Kurds want to make some amendments on the deal, and we are going to finish soon, Thursday to be exact. We do not want to impose any name from our side regarding the post of the parliament speaker. We want the Sunnis to nominate some people for this post, but until now they have not done this," al-Dabagh said.
Sunni Arab negotiators at Tuesday's meeting included interim President Ghazi al-Yawer — a possible choice for parliament speaker — the Iraqi Islamic Party and Iraqi nationalist leader Adnan Pachachi.
Sunni Arabs, who make up only about 20 percent of the population but were the dominant group under Saddam's regime, largely stayed away from the elections — either to honor a boycott call or because they feared being attacked at the polls by insurgents.