MUQDADIYA, Iraq » The orange archway at the entrance to this farming community welcomes visitors in "peace." The lush palm groves are heavy with ripe dates. For generations, Shiite and Sunni families worked the land, earning a living from their sheep and cows, their wheat fields and lemon trees.

On a recent morning, though, the only talk was of how to stop them from killing one another.

The latest strategy: new concrete walls with separate entryways for the different sects.

"So there’s a Sunni way in, and a Shiite way in," Abu Jassim, a Sunni resident who recently fled his home after sectarian revenge killings by Shiite gunmen, explained to a local representative in Parliament.

During the worst of Iraq’s carnage over the last decade, this area of Diyala province, a mixed region where Shiites, Sunni Arabs and Kurds still compete for power, faced killings and displacement. But what is happening now, villagers say, is worse — what one Western diplomat described in an interview as "Balkans-style ethnic cleansing."

Iraqi leaders worry that the violence here may be a sign of what awaits the rest of the country if the government cannot quell the growing mayhem that many trace to the civil war in Syria, which has inflamed sectarian divisions, with Sunnis supporting the rebels and Shiites backing the Assad government. Attacks have become more frequent this year, with major bombings becoming almost a daily occurrence. The violence countrywide has increased to a level not seen in five years, according to the United Nations, reinforcing fears that the type of sectarian warfare that gripped the country in 2006 and 2007 will reignite.

Here in this town, perched in the Tigris River valley on the way from Baghdad to the Iranian border, it already has.

It started in mid-July, when a fragile tranquility was shattered after a teenage boy, in a baggy T-shirt concealing a vest of explosives, walked into a Shiite funeral tent and detonated himself while mourners ate a dinner of lamb, rice and tomato soup.

The bombing was blamed on a resurgent al-Qaida in Iraq, and the bomber, it emerged, was a member of the local Sunni tribe, inflaming not just sectarian hatreds but local tribal rivalries.

In the days after, locals say, Shiite gunmen, some with ties to militias, others out for tribal justice, terrorized Sunni neighborhoods, killing some and demanding that others leave.

"It’s worse than anything that ever happened before," said Ali Jassim, another displaced resident, who, like others interviewed for this article, gave only an informal name, withholding his full name for safety reasons. "It was people attacking at night with machine guns, not considering if there were kids or women or old men."

Ali Jassim said he cowered in his chicken coop with his wife and children as gunmen fired on his home shouting: "You are Sunni, you don’t belong here. We will kill you if you don’t leave." The next morning, he packed some clothes and mattresses into a minivan and fled to a safer place, leaving his chickens and sheep behind.

He had lived in that house since 1966, staying even during the worst days of the sectarian war, but now says he will never go back.

Other residents received fliers on their doorstep, under the name of a prominent Shiite militia and wrapped around a bullet, telling them to leave or be killed, according to residents, officials and a report by Human Rights Watch.

The increasing role of Shiite militias here is a potentially ominous barometer of the country’s stability, an indication that the Shiite majority may have decided it is time, once more, to fight back against the Sunnis.

Even after the Sunni insurgency was tamed in 2007, there was less violence but no reconciliation, and al-Qaida kept up bombings aimed at restarting a sectarian war. But the Shiites, who are in charge of the government and security forces, mostly refrained from a violent response. The Shiite prime minister, Nouri al-Maliki, claimed to be a leader of all Iraqis, burnishing his nationalist credentials by taking on the Shiite militias in several military operations.

But now that calculus is changing: the militias, some of which answer to Iran, are re-emerging to protect their sect, believing that the security forces are unable to do so.

And the events that have unfolded in Muqdadiya, while the most vicious incidents of sectarian bloodletting, are not isolated: Latifiya, for instance, a Sunni-dominated area in south Baghdad, has seen the slaughter of entire Shiite families recently. And on Wednesday night, the Baghdad office of the United Nations issued a statement saying it was "gravely concerned" about recent forced displacements of Sunnis in southern Iraq and ethnic Shabaks in Nineveh Province in the north.

As Sunni families have fled Muqdadiya — at least 365 families have left, according to a government official — locals say militiamen have burned agricultural lands, shut off electricity, killed farm animals and poured cement into irrigation canals, in an effort to assure they would not return. And the violence continues: according to a local official, bombs recently destroyed two vacant Sunni homes.

Nahada Daini, a Sunni member of Parliament, is trying to prevent her hometown from descending into a maelstrom of violence.

On a recent morning, a group of Sunni villagers gathered in her reception hall to tell their stories and ask for protection so they can return to their homes. In the background, Secretary of State John Kerry and President Barack Obama appeared on a television screen, making their case to bomb Syria, whose war has increasingly destabilized Iraq. One man said his family had lived here for a century and a half, since the days of the Ottoman Empire, but was now being told that this was Shiite land.

Since the bombing of the funeral in July, the Iraqi security forces have been raiding homes in Sunni neighborhoods, casting a wide net in search of al-Qaida terrorists. They have restricted the movements of Sunni residents who stayed behind, making it especially difficult for them to drive vehicles from their neighborhoods, Daini said.

New blast walls have been put up around a central market that sits between Sunni and Shiite areas. She said local policemen that she suspects are members of a Shiite militia had tried to prevent Sunni men from even visiting the market, fearing they would set off bombs. The women are forced to walk long distances to shop.

In describing the situation, she invoked a potent symbol of Arab grievance.

"We call it Gaza," she said.

In Daini’s reception hall, three women in black abayas sat off to the side. One said her son had disappeared; another’s husband was missing.

Through tears, one of the women, who called herself Umm Jozsef, recalled the worst times of the American occupation and the sectarian grievances it unleashed. "It’s exactly the same," she said. "It’s the next episode, the continuation. But it’s getting even worse."

She added, "Since the Americans left, it’s like wild dogs here."

Days after their families fled their villages, a group of women went back to check on things, to see if their animals were alive, to water the crops. They were met at the edge of their village by a group of armed men, some of whom were young neighbors, the sons and grandsons of men who had once farmed next to the women’s fathers and grandfathers.

"Unfortunately, they forgot about all the old days," said one of the woman, Umm Ahmed.

As the violence receded in recent years, local communities began a halting process of reconciliation. "We thought this was all behind us," Umm Ahmed said. "We had started healing and becoming friends again. We went to each other’s funerals and weddings.

"Until the suicide bombing happened, we were becoming friends again."

Prominent members of the Shiite community, including Sheik Jathban Adnan al-Tameemi, attended the funeral that was struck by the suicide bomber, but he had left early. Sitting in his big meeting room recently, where he recalled once holding a "useless" meeting on reconciliation with Sunni tribal chiefs, Tameemi flipped through an album with photographs of him in his compound with friends from the American military. He still writes emails to them, his son translating.

"I’m so embarrassed to tell them what is going on here," he said. "I still have hope that they might come visit me, so I don’t want to discourage them."

For many young men over the last decade, sectarian identity has come to override tribal loyalties, eroding the authority of men like Tameemi and enabling the rise of militant groups.

On the Sunni side, the sheik said, "Qaida is not able to control the heads of the tribes, but they control the young men." On his side, he said, "they know it’s difficult for us to control our young people."

Still, he would not disavow the actions of his tribesmen, explaining that notions of tribal justice demanded that action be taken. But he appealed for calm, and said that once several suspects in the bombing attack were turned over to the authorities, "then the families can go back."

When asked about the involvement of militias, he said: "The sons of our tribes belong to many organizations. They have had their sons and fathers killed and were defending their tribe."

He said that young men had become more radicalized in recent years, as losses and suffering mounted, and that the next generation of militants might be more extreme than those who fought the sectarian war, which he worried might be starting all over again in his backyard.

"The problem of Muqdadiya," he said, "could spread through Diyala, to Baghdad, to all of Iraq."

© 2013 The New York Times Company