BAGHDAD, Iraq --The war in Iraq has entered a bloodier phase, with the killings of Iraqi civilians rising significantly in daily sectarian violence while American casualties have steadily declined. The increased violence is spurring tens of thousands of Iraqis to flee mixed Shiite-Sunni areas.
The new pattern, detailed in casualty and migration statistics from the past six months and in interviews with American commanders and Iraqi officials, has led to further separation of Shiite and Sunni Arabs, moving the country toward a de facto partitioning along sectarian and ethnic lines - an outcome that the Bush administration has doggedly worked to avoid over the past three years.
The nature of the Iraq war has been changing since at least the late autumn, when political friction between Sunni Arabs and Shiite Arabs rose even as American troops began implementing a long-term plan to decrease their street presence. But the killing accelerated after the bombing Feb. 22 of a revered Shiite shrine, which unleashed a wave of sectarian bloodletting.
About 900 Iraqi civilians died violently in March, up from about 700 the month before, according to military statistics and the Iraq Coalition Casualty Count, an independent organization that tracks deaths. Meanwhile, at least 29 American troops were killed in March, the second-lowest monthly total since the war began.
The White House says that little violence occurs in most of Iraq's 18 provinces. But those four or five provinces where the majority of the killings and migrations take place are Iraq's major population centers, generally mixed regions that include Baghdad and contain much of the nation's infrastructure - crucial factors in Iraq's prospects for stability.
Since the shrine bombing, 30,000 to 36,000 Iraqis have fled their homes because of sectarian violence or fear of reprisal, say officials at the International Organization for Migration, based in Geneva. The Iraqi Ministry of Displacement and Migration estimated that at least 5,500 families have moved, with the biggest group being 1,250 families settling in the Shiite holy city of Najaf after leaving Baghdad and Sunni-dominated towns in central Iraq. The families are living with relatives or in abandoned buildings, and a crisis of food and water shortages is starting to build, officials say.
"We lived in Latifiya for 30 years," said Abu Hussein al-Ramahi, a Shiite farmer with a family of seven, referring to a village south of Baghdad that is a stronghold of the Sunni Arab insurgency. "But a month ago, two armed people with masks on their faces said if I stayed in this area, my family and I would no longer remain alive. They shot bullets near my feet. I went back home immediately, and we left the area early next morning for Najaf." Al-Ramahi's family and other migrants are squatting in a derelict hotel in the holy city.
"It's almost a creeping polarization of Iraq along ethnic and sectarian lines," said Anthony H. Cordesman, a military expert at the Center for Strategic and International Studies in Washington.
In the chaos, he said, "We see a slow, steady loss of confidence, a growing process of distrust which you see day by day as people at the political level bicker. Everything has become sectarian and ethnic."
The shifts in violence and migration patterns are fueling discussion about whether Iraq is devolving into civil war. Although that determination may be impossible to make in the short term, the debate could increase the political pressure that President Bush is facing at home to draw down significantly the force of 133,000 American troops here. Even if American deaths keep falling, polls show that the American public has little appetite for engagement in an Iraqi civil war.
Commanders in Iraq say the insurgent groups in the country have shifted the focus of their attacks in an effort to foment civil war and undermine negotiations to form a four-year government. "What we are seeing him do now is shift his target from the coalition forces to Iraqi civilians and Iraqi security forces," said Maj. Gen. Rick Lynch, a senior spokesman for the American command. "The enemy is trying to stop the formation of this national unity government; he's trying to inflame sectarian violence."
It is not clear whether this change in the nature of the war is permanent. But since the shrine bombing, Shiite cleric Muqtada al-Sadr's thousands-strong militia has been focusing its wrath on Sunni Arabs; the militiamen are accused of killing hundreds in late February alone. As for the traditional insurgency, some hard-line Sunni Arab officials say the Sunnis are more concerned now about the growing power of religious Shiite leaders, their militias and Iran than about the American presence.
The results of the December elections showed that the religious Shiite coalition, backed by Iran, will almost certainly control the new government and that the Sunni Arabs, no matter their participation in the vote, will face Shiite rule for years. That Sunni-Shiite tension sharpened when insurgents destroyed the golden dome of the Askariya shrine in Samarra in February, and vengeful Shiite militiamen rampaged through Baghdad and other cities.
American officials say the solution to the sectarian bloodshed lies in the Iraqis' quickly forming a national unity government, with representatives of all major groups in Iraq checking one another through compromise.
But the mass migrations could mean that Iraq's political groups will have little incentive to compromise as they separate into their enclaves. For example, at least 761 families have settled in Baghdad after moving from Anbar province and other Sunni-dominated areas to the west, according to Iraqi government statistics. The same is happening on the Sunni Arab end - there are reports of 50 families moving from Baghdad to the Sunni enclave of Fallujah.
Aid groups have been handing out mattresses, blankets, cooking sets and other gear to families throughout central and southern Iraq.
"The situation for those displaced won't be resolved anytime soon," said Jemini Pandya, a spokeswoman for the International Organization for Migration.
The migrations are partly caused by the fear of partisan Iraqi security forces, many of them trained by the Americans.