Along the battle line north of Falluja, small units of Shiite fighters are raining mortar shells and rockets down on the city and its Islamic State occupiers. Militia graffiti is scrawled in red paint along a network of low walls cratered by bullets and bombs, and a wailing ambulance siren signals another load of wounded bound for treatment away from the front.
The battle for Falluja has become entrenched outside the city itself. Iraqi forces surrounding the area have been bogged down by a fierce Islamic State counterattack. A few civilians managed to escape the city as the fighting closed in, but the status of tens of thousands still trapped there is an urgent question.
Some parts of the extended battlefield are lush with date palm trees and almost bucolic, familiar to anyone who watched television images of American Marines fighting over the same territory more than a decade ago. But mostly, the land is brown and parched, scarred by the fighting. A charred tank, split in two, sits at an intersection, and smoke is always rising in the distance, from an airstrike, a mortar or a car bomb.
The landscape has also been gutted by an elaborate network of tunnels — some of which have been hit in recent days by American airstrikes — that the Islamic State was able to construct while it held the area for more than two years.
To get close to the front, a New York Times reporting team met officials from the Badr Organization, a longstanding Shiite militia backed by Iran, at a street corner in Baghdad outside a shawarma shop on Sunday morning. Our cars joined theirs in a small convoy, and, whipping past the traffic-choked checkpoints, we made it to a base east of Falluja in about an hour.
Within the base, Iraq’s fragmented security forces occupied different areas: Iranian-supported militias in one place; the elite Iraqi Army counterterrorism forces, which work closely with the United States, in another; and Sunni policemen from Falluja, who are scheduled to hold the city once it is taken from the Islamic State, in yet another space, some of the men lounging in tank tops or fixing their vehicles.
Near the front, Hadi al-Ameri, the Badr Organization’s leader, spoke of the forces’ progress in Falluja’s outlying areas. “I am amazed at the advancements so far,” he said. “We expected it to be a long vicious battle.”
Still, the real fight — taking the city street by street — has not yet begun, and Mr. Ameri said the battle might be slowed to allow civilians to leave.
“We have a big concern for the lives of civilians inside Falluja,” said Mr. Ameri, mindful of the sectarian tensions that have been heightened with the battle, as a mostly Shiite force converges on a Sunni city. “There may be a delay to allow civilians to leave.”
That would parallel what happened during the first battle for Falluja, in April 2004, when American forces began assaulting the city, only to pull back because of concerns about civilians being killed. Then, Falluja became a byword for the United States’ failure to pacify a growing insurgency, and it was not until seven months later, in November, that Marines moved in and cleared the city in a battle that cost nearly 100 American lives.
The battle for Falluja now unfolding is being fought by a jagged constellation of government security forces, Shiite militias and Sunni tribal fighters. They are closing in on the city from the north and south, but not yet fighting for its center.
Still within Falluja are an estimated 50,000 civilians, long cut off from shipments of food and medicine by a government siege and now under artillery fire as the front lines have tightened around the city.
The Norwegian Refugee Council on Tuesday warned of a “catastrophe unfolding in Falluja,” saying that humanitarian conditions were “rapidly deteriorating as fierce fighting intensifies.” And the United Nations, based on informers in the city, warned Tuesday that civilians were being killed from shelling by pro-government forces, including seven members of one family a few days ago.
Lise Grande, the top United Nations humanitarian official in Iraq, said in an interview, “I am desperately worried about what is happening to civilians in Falluja.”
Ms. Grande said that informers inside the city had told the United Nations that Islamic State fighters were moving families to the city center to serve as human shields. Families who have been able to leave have reported severe food shortages and a lack of clean water, raising concerns, she said, of a cholera outbreak.
About 3,700 people, mostly from the outlying areas of Falluja, have reached safety over the past week, the United Nations said. An additional 500 men and boys over the age of 12 have reached government lines but are being held by the Iraqi authorities for questioning about any potential links to the Islamic State, also known as ISIS or ISIL.
Falluja has been closed to the world since the Islamic State captured it more than two years ago, as a steppingstone to its broader conquest of northern and western Iraq.
A glimpse of the darkness that has grown inside emerged early Tuesday, when two women from the Yazidi religious minority, believed to have been captured in northern Iraq by the Islamic State and held in Falluja, possibly as sex slaves, reached safety by boat across the Euphrates River.
Vian Dakhil, a Yazidi member of the Iraqi Parliament, traveled to Baghdad on Tuesday to meet the women, and said she believed that more Yazidi women were trapped inside the city. “I don’t know the exact number, but I’m sure there are many, many more,” Ms. Dakhil said in an interview.
Standing in a field of scrub and palm trees on Sunday, near the front lines, Col. Sadiq Jaleel, of the federal police, said the Islamic State was unleashing its full arsenal against his men: snipers, booby-trapped houses, roadside bombs.
He stressed that his men, a mortar team arrayed around him, amid open crates of shells, were advancing slowly to protect civilians.
“The fighting has been vicious,” the colonel said. But he quickly added, referring to the populated heart of Falluja, “the battles in the residential areas will be more difficult.”
Humanitarian officials in Iraq believe they are racing against time to avert what they worry could be a blood bath should Iraqi forces storm the city center. Those fears were heightened on Monday morning, when Iraq’s United States-backed counterterrorism forces left their bases and advanced from the south toward the city.
Statements that commanders gave to the news media on Monday falsely asserted that they had entered the city and were fighting for it. But on Tuesday it was clear that their advance had stalled in the face of stiff resistance from the Islamic State.
The battle for Falluja has caught the public’s attention after a stretch of political turmoil that saw protesters storm Baghdad’s Green Zone and Parliament. Accordingly, the battle is also being waged in the Iraqi news media, and the various forces involved have all kept up a patter of statements claiming battlefield successes that, in some cases like on Monday, have yet to happen.
On Tuesday afternoon, as it became evident that no quick victory was at hand, Iraq’s Joint Operations Command, a central hub for the army, federal police and militias, urged the news media to be careful: “We warn all of the mass media to be accurate with the news about the military operations for the Falluja battle, and not to be hasty in publishing information and news and to check the sources of the news before publishing them.”