The group returned within the hour after a speaker, Iraqi Christian Ibrahim Menas al-Youssefi, apologised for comments regarded as insulting.
Sunni delegate Shehab al-Dulaimi said the conference had resumed after the Arab League conveners said his criticism of fellow delegates would be struck from the record.
In his speech, al-Youssefi had accused fellow delegates of being US stooges saying the entire Iraqi political process was illegitimate and orchestrated by Washington.
Storming out of the meeting Shia legislator Jawad al-Maliki said such comments were insulting towards the Iraqi people and towards the constitution "on which several million Iraqis have voted".
He added: "They want the situation in Iraq to go back to the way it used to be so that the mass graves can return."
The incident highlighted the difficulties of trying to bridge deep divisions among delegates at the meeting, called by the Arab League in preparation for a bigger reconciliation conference to be held later in Baghdad.
Earlier Iraqi President Jalal Talabani told the conference that violent extremists and associates of former president Saddam Hussein have no part in Iraq's political process.
"Our national unity ... does not include under any circumstance the murderers and criminals among the followers of the old regime, who left us mass graves, or among the takfiris (religious extremists)," Talabani said.
The landmark meetings, due to lay the basis of a reconciliation conference in Baghdad, came against a tense domestic backdrop, after bombings in Iraq over the past 24 hours killed more than 90 people.
Sunnis claim marginalisation
Egyptian President Hosni Mubarak said national reconciliation was the key to a successful political process in Iraq and to a gradual end to the presence of foreign forces.
"The password for building the new Iraq ... is ensuring that all the sons of Iraq take part, without exception or marginalisation," he added.
Al-Yawar said all Iraqis should
attend the conference
While Shia Muslim politicians condemned the violence, a leading Sunni politician said resistance was a legitimate response to US occupation.
Harith al-Dhari, the chairman of the Association of Muslim Scholars told the conference at the Arab League that the government was excluding people from jobs on ethnic and sectarian grounds.
One group, the Army of the Victorious Sect, ridiculed the Cairo conference in a statement on a website often used by fighters opposed to the presence of foreign troops in Iraq.
"This conference being held in Cairo while the Crusaders and their accomplices are killing Muslims is just like the other conferences that have sold Muslim honour and wealth for the lowest price to Crusaders and Jews," it said.
"Armed resistance arose as a reaction to occupation. It is legitimate and is not an innovation"
Association of Muslim Scholars
The Arab League arranged the conference out of alarm that Iraq, once a pillar of the Arab community, is descending into chaos and towards sectarian conflict.
The current Iraqi government is dominated by Shia and Kurds. Many Sunnis, whose community was politically dominant for hundreds of years, feel they have been pushed to the margins.
The differences of approach were evident in the priorities the politicians set in their speeches in the opening session.
Talabani and Iraqi Prime Minister Ibrahim al-Jaafari emphasised the misdeeds of their Iraqi opponents, while al-Dhari said the US and British occupation was the problem.
The talks came after more than
90 people were killed in bombings
"Armed resistance arose as a reaction to occupation. It is legitimate and is not an innovation. The popular support which the insurgents enjoy in many parts of the country exceeds what they enjoyed a year ago," al-Dhari said.
He called for a firm timetable for US and British withdrawal and dismissed the government's arguments for allowing them to stay while Iraqi forces build up their strength.
Breakthrough not expected
Vice-President Ghazi al-Yawar, a leading Sunni tribal leader, argued the talks would have benefited from wider participation. "All Iraqis should be here if we want our problems to be solved," he said.
Iraqi government spokesman Laith Kubba was pleased with the list of participants at the Cairo meetings but said it was too early to tell whether reconciliation was under way.
"We don't have too high expectations. The purpose of this meeting is to develop an agenda. If we reach an agreed agenda, this will already be a big step," he told AFP.
Analysts say they expect few breakthroughs in the three-day session in Cairo and that it will take much more than talks on the banks of the Nile to allay fears of a sectarian civil war.
"The Iraqi issue is extremely complicated. It needs many conferences and those going to Cairo should open their hearts and listen to others," said Imad Ali, a Sunni attending the
conference along with more than 50 Iraqi politicians.