FALLUJAH, Iraq – At a checkpoint outside militant-held Fallujah, hundreds of civilians who fled the fighting between Iraqi forces and the Islamic State group huddled late at night in packed mini-buses on the side of a highway as security forces separated out those suspected of supporting the extremists.
Six men sat blindfolded on the pavement, heads bowed patiently, beside a row of concrete barriers illuminated by the headlights of an SUV and a Humvee.
"They hold the men because they believe we all support Daesh," said a woman at the checkpoint, referring to the Islamic State by its Arabic acronym.
After an officer finished registering her and stepped away, she whispered to a reporter, "Of course there is support for Daesh, but it's not every family."
Since the Iraqi government launched its offensive May 22 to retake Fallujah from the Sunni-led extremists, the troops have been detaining all military-aged men for questioning as they flee the city west of Baghdad. They want prevent any of IS militants from slipping out among the civilians to fight elsewhere.
The soldiers, police and two intelligence officials took down the names of the six blindfolded men on the roadside before loading them onto a truck bound for a detention center. Officials at the scene said the screening would take only a few days, and those found to be innocent would be reunited with their families.
One of the few men allowed to go free was 53-year-old Hameed Hussein, whose poor health makes him look and sound much older. He said he believes that's the reason he was not detained, unlike his teenage sons.
Many residents from the Sunni majority city say it was the heavy-handed tactics of the security forces — including arbitrary arrests — that drove people to support the extremists when they took over Fallujah more than two years ago.
The Iraqi command said Sunday that key areas west of Fallujah had been taken and that Iraqi forces pushed deeper into the city from its southern edges. U.S.-trained counterterrorism forces, wary of coming street battles in the city, already are facing fierce resistance on the outskirts from well-entrenched militants.
Many front-line commanders view Fallujah as a nest of Sunni extremism, while its residents see the Shiite-led government as an occupying power. That sense of mutual distrust has confounded efforts to bring peace to the city ever since the 2003 U.S.-led invasion that toppled Saddam Hussein.
And that continued suspicion could hinder the latest push to bring Fallujah back under government control.
One senior Iraqi commander said support for the IS group among civilians is more widespread, and that once government forces move in, it will be hard to tell friend from foe. He spoke on condition of anonymity because he was not authorized to brief reporters.
In past campaigns, Iraqi forces have relied on fleeing civilians for intelligence as they push into IS-held territory, but the commander said he expects to gain little from Fallujah's residents, which could slow his troops' progress.
Enhanced screening of civilians, including the detention of fighting-aged men, is needed to prevent militants from escaping, officials said.
"It's the only way to keep the rest of the Iraqi people safe," said Yahya al-Muhamadi, an Anbar province council member working with civilians displaced from Fallujah.
Officials declined to say how many young men were being held. Amnesty International has estimated the number to be in the thousands, and it described the conditions in a facility it visited last month as "shocking."
The United Nations estimates that more than 40,000 people have fled Fallujah — including about 7,300 on Sunday and Monday, leaving about 50,000 people still trapped in the city. The Norwegian Refugee Council, which provides aid in Anbar, says few have been able to escape central Fallujah.
On Monday, an Iraqi government spokesman said an investigation has been launched into possible human rights abuses of civilians fleeing the city. Some Iraqi fighters suspected of violating human rights during the 3-week-old operation to retake the city have been arrested in recent days, said government spokesman Saad al-Hadithi.
He did not provide details on whether the fighters are from the army or government-sanctioned paramilitary forces, which are mainly made up of Shiite militias.
Local Sunni officials and human rights groups have accused Shiite militias of arresting, torturing and killing Sunnis who fled Fallujah and its outskirts. Anbar provincial Gov. Suhaib al-Rawi told reporters Sunday that 49 civilians were killed and 643 others have disappeared. The U.N. human rights chief said there were "credible reports" that people fleeing Fallujah faced physical abuse as they escaped.
Fallujah has been locked in a cycle of conflict since 2003, when it emerged as a bastion of the insurgency against the Americans. Militant attacks and bombings were followed by sweeping arrest raids, which further stoked local grievances. In 2004, U.S. troops launched two massive assaults on the city, where they fought their bloodiest battles since Vietnam.
There were a few years of relative calm starting in 2006 when local tribes allied themselves with U.S. forces against al-Qaida in the so-called Sahwa — or Awakening — movement. But after U.S. forces withdrew in 2011, the movement largely disintegrated amid neglect from Baghdad, and the cycle of attacks and arrests resumed.
A 30-year-old Fallujah resident said that in the years before the IS takeover of the city, Iraqi forces would regularly sweep in and arrest fighting-aged men at random. "At that time, the government was just taking anyone and then forcing them to confess to something they didn't do under torture," he said. Both the man and the woman who was registered at the checkpoint spoke on condition of anonymity because they feared for the safety of relatives still inside the city.
When IS militants entered Fallujah in January 2014, months before their main sweep across northern and western Iraq, many residents welcomed them as liberators.
"At the beginning, at least, Daesh didn't kill people or arrest them for no reason like the government did," the 30-year-old man said. "They had clear rules that you could follow to protect yourself."
Maria Fantappie, senior Iraq analyst at the International Crisis Group, said that while it's impossible to gauge how much support IS has in Fallujah, it was never a grass-roots movement. Instead, the extremists allied with local and tribal leaders, whose support was based more on a "political opportunity than an ideological affiliation," she said.
"When you have been politically marginalized," she added, "you are going to try and find other allies who will empower you."
Life grew difficult after IS seized Fallujah and government forces shelled the city. In recent months, the military and allied Shiite militias have gradually encircled it, cutting off highways and sending food prices soaring. But residents say IS still enjoys scattered support.
"Like on each street, there is only one house that supports Daesh," said the 30-year-old man, "and even inside that house, maybe only the son supports them, not the entire family."
Abdul-Zahra reported from Camp Tariq, Iraq.