For much of the past two years, about 1,000 Sunni families have lived peacefully alongside a Shiite majority in a northern Baghdad neighborhood with grease-stained repair shops and streets of sand.

But all that has changed this spring, Sunnis and local public officials say. More and more, the Hurriya neighborhood is being dominated by Shiite troublemakers who had been largely sidelined as long as U.S. troops were the dominant force in Iraq.

Now, Sunni men talk about a “death calendar.” In the past six weeks, they say, a Sunni man has been executed in the neighborhood about every seventh day, in what they interpret as an intimidation campaign by Shiite extremists.

“Here, they don’t use silencer pistols to kill you, because they are not afraid,” said Sabah Alwan, sitting in front of a picture of his nephew, Adil Rasheed Batta, who was shot nine times in the head and chest May 17. “There is no one to face them.”

The violence and the efforts that began last week to quell it have raised new questions about what lies ahead in Iraq, which is facing the departure of U.S. forces at a time when the government remains hobbled by political infighting, largely along sectarian lines.

In recent months, Iraq’s security forces have focused primarily on combating Sunni-dominated extremist groups, such as al-Qaeda in Iraq, which they blame for headline-grabbing attacks. The security forces report to Prime Minister Nouri al-Maliki, a Shiite.

But local officials in Baghdad say that Shiite militia groups are regrouping in a way that also poses a severe threat.

“These were well-planned incidents and were implemented in a professional way,” said Khammas al-Garawi, head of Hurriya’s local security committee. “I believe the directors are both inside and outside Iraq,” Garawi said, in an apparent reference to Shiite-dominated Iran, which has provided support for some Shiite militias.

‘We have no choice’

In a neighborhood where many Sunni mosques were burned or ransacked during the height of Iraq’s ethnic struggles in the mid-2000s, the problems that arise when neighbors kill one another are hardly new.

At one time, more than 25,000 Sunni families called Hurriya home, living not far from the plantations that their ancestors founded before Baghdad became a sprawling city.

Most never returned after being run out of town as the regime of then-President Saddam Hussein, a Sunni, collapsed in 2003.

The families that did return in recent years said they were promised that Hurriya, a neighborhood of 450,000 residents, would be a model for reconciliation.

Instead, Sunni residents say, envelopes containing bullets have been left at their door since March. Warnings such as “Dirty Sunni, leave the area” or “Your blood is wanted” have been scrawled on homes and walls. Windows have been shot out. And Sunni children are being kidnapped for ransom, according to town officials and family members.

“We have no choice but to leave this area,” said Hasan Albatta, adding that hundreds of Sunni families are preparing to move. “We wish we could stay, but they don’t let us.”

Although few expect Iraq to slip back into civil war, U.S. and Iraqi officials believe that tension in Hurriya reflects the government’s broader challenge to contain both Shiite and Sunni militias amid questions about the reliability of the country’s security forces.

Maj. Gen. Jeffrey S. Buchanan, the chief spokesman for U.S. forces in Iraq, said Iranian-backed militias such as Kataib Hezbollah, Asaib Ahl al-Haq and the Promised Day Brigade “are responsible for the killing and injury of Iraqis and sowing the seeds of instability as Iraq tries to move forward.”

“My concern is that these groups will remain in Iraq after the U.S. forces have departed, and they will be aligned with Iran and continue to act in Iran’s interests,” said Buchanan, adding that he suspects an Iranian-backed militia is responsible for a bombing Thursday in Baghdad that killed an American working for the U.S. Agency for International Development.

Many Sunnis accuse Maliki of fanning sectarian tensions, noting that he permitted radical Shiite cleric Moqtada al-Sadr to parade his Mahdi Army militia through Sadr City last month. More recently, Maliki’s government helped orchestrate a public campaign calling for the execution of several Sunni men suspected of killing 70 Shiites at a wedding in 2006.

But Ibrahim al-Mashhadani, an adviser to Iraq’s reconciliation minister, attributes the violence in Hurriya to a small percentage of “bad guys” from “outside the country” who still “have the brains of dark times.”

Yet, Iraqi security forces in the neighborhood have appeared unable or unwilling to confront Shiite extremists, including a militia that officials say is so bold that it has begun extorting an illegal tax on some home sales.

Intimidation campaign

Motorists seeking to enter Hurriya sometimes have to wait up to an hour at Iraqi army checkpoints, and Iraqi soldiers in U.S.-made Humvees patrol narrow streets clearly designed for donkeys instead of vehicles.

Despite the heavy security, about 20 Sunni tribal leaders were carrying the names of men suspected in the recent killings when they showed up last week at the Sunni Endowment, the sect’s financial and philanthropic wing, seeking justice for the violence.

“All of the incidents and killings are for sectarian reasons,” said one neighborhood official, who spoke on the condition of anonymity because he fears for his safety. “Even security members at the checkpoints are afraid of those militia members.”

Last month, a young man sitting in front of his house was shot by two men on a motorcycle, according to Sunni tribal sheiks.

A few days later, Batta’s 6-year-old son was kidnapped on his way to school. Alwan said that a ransom was paid for the boy’s safe return but that Batta was still dragged out of a restaurant four days later and fatally shot in the street.

“Even the army members were not brave enough to pick up his body or even cover his body,” Alwan said. “A brother of mine had to go and bring his body home.”

In early June, residents say, a third Sunni man was ambushed by attackers with assault weapons when he stepped out of his car.

In the fourth slaying, residents say, a Sunni day laborer was shot near a military checkpoint. A fifth man died a week later when four gunmen burst into his home and shot him in front of his family.

The sixth killing occurred Tuesday, according to Sunni residents and officials.