Iraq's most influential religious leader, Grand Ayatollah Ali Sistani, on Thursday urged his followers to adopt a draft constitution scheduled for a nationwide referendum next month, offering crucial support for a document that will give legitimacy to the fledgling Iraqi government.

Observers had been watching to see whether Sistani would weigh in on the political process. Millions of Shiites followed his call in January to vote in the country's first democratic elections in nearly half a century, which gave the Muslim sect a majority in the new government.

If two-thirds of the voters in any three of Iraq's 18 provinces reject the constitution, a new government must be formed and the process of writing the document would start again.

Some Sunni Muslim clerics and politicians have urged their followers to vote down the document, complaining that they did not have adequate representation in drafting it. Sunnis, the favored group under ousted president Saddam Hussein, are estimated to make up nearly 20 percent of the population and form the majority in four of the country's 18 provinces.

Meanwhile, violence across the country killed about a dozen Iraqis.

Two attacks occurred in the Niariya neighborhood in eastern Baghdad. In the first incident, armed men wearing police uniforms stormed the house of a Shiite family, witnesses said.

In the ensuing gun battle, three men were killed and a woman was wounded as she ran from the house screaming that the armed men were criminals, not police. Neighbors said they did not know whether the men, who had two-way radios, were police or were wearing stolen uniforms. The attackers kidnapped a resident as they fled the area.

An hour later just down the street, gunmen killed two brothers, who were Christians, and two other men as they drove to work. The slain men were guards for the former minister of displaced persons and immigrants under the interim government of Ayad Allawi, a spokesman said. Family members confirmed the deaths.

"My God, he was alive one hour ago," Hussam Ghadban, a resident, said of one of the brothers. Minutes before he was killed, according to Ghadban, the man had said: "What a silly life we live in. Where should we go to avoid this violence?"

The attacks occurred in the same area where 26 children were killed in a suicide bombing two months ago. Neighbors expressed outrage at the Iraqi government, calling it a failure for not protecting the people.

"It is a very difficult life," said Anwar Ishac, a cousin of the slain brothers. "We cannot live in this country. That is why everyone, not only the Christians, is leaving the country. It's not safe to go to work. It's not safe to sit at home. If this government cannot do anything to protect us, let them leave. Even the American Army cannot protect us."

Meanwhile, Prime Minister Ibrahim Jafari, in his first news conference since returning from a two-week visit to the United States and Britain, told reporters that media organizations were supplying misinformation about the progress being made in Iraq.

"Many might not understand Iraq as accurately as it should because of the media we suffer from," he said.

Jafari also blasted the Syrian government for not doing enough to stop insurgents from crossing into Iraq. "It is not an accusation," Jafari said. "It is reality that there is an infiltration." He said the restoration of normal relations with Syria depended on "the commitment of the Syrian side and the cooperation to control the borders and security."

Jafari played down tensions with Britain over a recent incident in Basra in which British forces stormed an Iraqi jail to free British commandos who were arrested on suspicion of planting explosive devices and shooting at police. "I don't think it will be an obstacle that we cannot overcome," Jafari said. "We should learn from this and make sure it doesn't happen again."

Hundreds of residents and police officers demonstrated in Basra on Wednesday, two days after Iraqi police arrested the Britons. Five civilians were killed in the clash, including two who died of their injuries Wednesday, according to hospital authorities.

Elsewhere in Iraq, Saad Abdullah Suilayman, a police commissioner, was killed when unknown gunmen opened fire on his car in the northern city of Kirkuk. Suilayman was an Arab resident of the ethnically diverse city, said Col. Adel Zainlabideen, a spokesman for the Iraqi police in Kirkuk. Two of the commissioner's cousins were wounded in the attack before the gunmen fled the scene, the spokesman said.

In Baqubah, about 35 miles northeast of Baghdad, police Col. Abbas Fadhil was killed by unknown assailants on his way to work, according to his driver, Kareem Hussein Kadhim. The assailants, traveling in two cars, stopped the vehicle in which Fadhil was riding and asked him to step out. When Fadhil acknowledged who he was, the men sprayed him with bullets. The driver said he tried to stop the assailants but was shot twice in the leg.

In Latifiyah, south of Baghdad, armed men killed a resident who was working for the Iraqi army. Capt. Muthana Ahmed, a police spokesman, said insurgents forced the man to lie in the road and then ran over him, crushing him to death.

Staff writer Jackie Spinner in Baghdad and special correspondent Saad Sarhan in Najaf contributed to this report.

An Iraqi policeman mans a machine gun during clashes with insurgents near a secondary school in western Baghdad. Attacks by gunmen killed a dozen people across the country.