Gunmen on Tuesday killed two Sunni Arab members of the commission writing Iraq's new constitution, witnesses and political associates said. They were among at least 27 Iraqis killed Tuesday across the country.

The commission members, Mijbil Sheikh Esa and Dhamin Hussein Ubaidi, were killed in Baghdad less than a month after they and 13 other Sunnis had been brought into the constitution-writing process in a bid to draw support away from the country's insurgency.

The gunmen approached the car in which Esa and Ubaidi were riding from the front and behind on a street in the Karrada district, a witness said. A man traveling with the commission members also was killed and another was wounded.

Drafting a constitution is the primary task facing the Iraqi legislature that was elected in January. The process was delayed for months as political factions sought ways to include more Sunni Arabs, who had largely boycotted the January vote, leaving them with little representation in the 275-member National Assembly or on the constitutional committee.

The Shiite Muslim-led government of Prime Minister Ibrahim Jafari and various political factions had hoped that by including more Sunnis in politics they could siphon support away from the largely Sunni-driven insurgency that has ravaged Iraq for two years. But insurgents have targeted many Sunnis who have accepted positions in the government.

"We received threats a month ago," said Saleh Mutlaq, a spokesman for the National Dialogue Council, a Sunni political group to which Esa and Ubaidi belonged. "Now they've decided to assassinate all the committee's Sunni members, so that no Sunni participates" in the constitutional process, he said. The committee is scheduled to complete a draft constitution by Aug. 15. A referendum on the document is set for Oct. 15, and legislative elections are planned for December.

The attack occurred while the constitutional commission was meeting in Baghdad's heavily fortified Green Zone. The commission's head, Humam Hamoudi, adjourned the session when he received the news, the Associated Press reported. Hamoudi, a Shiite cleric, condemned "this criminal act that targeted the Sunni Arab brothers. Terrorism is against everyone and not against a specific sect."

Hours before the killings, President Jalal Talabani met with Hamoudi and encouraged the panel to meet the August deadline, according to a statement released by Talabani's office. Talabani said that the constitution "should represent all the Iraqi people and maintain their legal rights," the statement said.

Most officials involved in the constitutional process have expressed optimism that the deadline will be met, and it was not immediately clear whether the assassination of Esa and Ubaidi would affect the committee's progress.

In violence elsewhere in Iraq, eight Iraqi workers were ambushed on their way to work at a U.S. military base in Khalis, about 40 miles northeast of the capital, said Ahmed Hasan, a spokesman for the nearby city of Baqubah. A minibus transporting the workers was cut off by two pickup trucks carrying armed men who fired into the vehicle, Hasan said. The gunmen also killed four Oil Ministry engineers when the engineers approached in another bus during the attack.

A roadside bomb just south of Baghdad on Tuesday killed two policemen, the Reuters news agency reported.

In the oil city of Kirkuk, about 150 miles north of Baghdad, two people were killed, including a policeman, and five were wounded by two roadside bombs. Farther north, in the town of Tall Afar, mortar attacks and gunfights killed at least eight people and wounded 13, police Capt. Amjed Hashim Taqi said. The firefights pitted insurgents against U.S. and Iraqi troops, Taqi said. The source of the mortar fire was not clear.

In London, the British Defense Ministry reported Tuesday that three British soldiers had been charged with war crimes for the inhumane treatment of Iraqi detainees. It was the first time British troops have faced war crimes charges stemming from the Iraq war, a ministry spokesman said.

A report issued by two research organizations in London concluded that nearly 25,000 civilians were killed between March 2003, the start of the Iraq war, and March 2005, based on an analysis of published news media reports. About 9,300 of those deaths occurred during U.S.-led military action, according to the report by Iraqi Body Count and Oxford Research Group. The analysis did not include data for the period since April, when deadly insurgent violence has escalated.

Special correspondent Dlovan Brwari in Mosul contributed to this report.