About 14 miles from Baghdad International Airport, a mortar shell landed with a thud. A second followed, closer, and then a third struck across the Iraqi army’s lines, as the Islamic State militants zeroed in on their target.

The volley of mortar fire outside the Baghdad suburb of Abu Ghraib this week was not unusual in itself; Islamic State fighters and the Iraqi army have regularly exchanged fire in this area for months. But now, officials worry that gains by the extremist group in neighboring Anbar province will provide momentum for an assault on the outskirts of the capital.

Mortar shells fired by the Islamic State have already fallen in central Baghdad in recent weeks, and suicide bombings have picked up pace — a wave of blasts killed at least 50 people in and around Baghdad on Thursday, local media reported. While the army is holding its ground around the capital’s perimeter, Abu Ghraib is seen as a weak point, and sympathy for the radical fighters is growing here, residents say, because of the heavy-handed actions of Shiite militias.

Despite U.S. and allied airstrikes intended to crush them, the Sunni extremists have been steadily consolidating power in the majority-Sunni province to the west. Islamic State fighters continued to advance Thursday, closing in on the Anbar town of Amriyat al-Fallujah, one of the last in the province still controlled by the government. Local officials begged the government to send reinforcements, warning that the town could be overrun in a matter of hours.

‘The gate of Baghdad’

“If Anbar falls, it’s going to have a huge impact, for us and all Baghdad,” Gen. Ali al-Majidi, a commander with the Iraqi army’s 6th Division, said Tuesday as he visited troops on the front line near Abu Ghraib. “This is the gate of Baghdad; if they took this area, they could mortar the airport.”

An Iraqi solider crouches by an earthen berm dug at a front line with Islamic State militants. Despite regular exchanges of fire, the line has not moved since May. (Loveday Morris/The Washington Post)

Iraqi officials complain that media reports claiming that the Islamic State has advanced on Baghdad through Abu Ghraib are inflammatory. But there is no doubt the security situation around the capital is precarious.

On Oct. 1, four mortar shells struck inside the Green Zone, a fortified area in central Baghdad filled with foreign embassies and government buildings, according to a U.S. Embassy security official, who declined to be identified. The rounds fell a few hundred yards from the U.S. Embassy and followed another mortar attack a week earlier, he said.

Brig. Gen. Saad Maan, spokesman for Baghdad Operations Command, confirmed that mortar fire had hit inside the Green Zone but said the shells landed on “empty space without any buildings.” He declined to give further details but said an investigation was underway to determine its source. He stressed that there have been no further incidents.

But Islamic State mortaring is becoming increasingly frequent, with five rounds targeting the Shiite neighborhood of Shula on Thursday, according to security officials. The Shiite neighborhood of Kadhimiyah has also come under mortar fire in recent weeks.

Rear Adm. John F. Kirby, a Pentagon spokesman, said Wednesday that there is “no question” that the Islamic State wants to put pressure on Baghdad but that the extremist group does not pose an “imminent threat” to the city’s security.

“Anbar is important, and it is proximate to Baghdad. That is not in any way analogous to Baghdad falling,” said another senior U.S. official in Washington, speaking on the condition of anonymity to discuss security matters. “That is not going to happen.”

But, he added, “the more terrorists that they have around Baghdad, the more they can cause mischief.”

A child plays with a stick in Abu Ghraib market, on the outskirts of Baghdad, where life continues as normal just a few miles from the front lines. (Loveday Morris/The Washington Post)

Maan also said that the Islamic State doesn’t have the capacity to seriously penetrate the capital. But maintaining a buffer zone is essential in protecting Baghdad from longer-range attacks like those on the Green Zone. And there are worries that the Islamic State will find sympathizers in the Sunni-majority belt that rings the capital, including Abu Ghraib.

Underlying tensions

About 200,000 people live in Abu Ghraib and the surrounding villages and agricultural areas. On Tuesday, Abu Ghraib’s main market buzzed with activity, and there was no sign of violence. Merchants yelled the price for pomegranates and tomatoes, as families shopped for food and clothing in the tangle of stalls. But local people said there are underlying tensions that could lead to support for the Islamic State here.

Residents said Shiite militias moved into the area in June, after the northern city of Mosul fell to the Islamic State, at the beginning of its rapid advance across northern and western Iraq. With the Iraqi army in crisis, militias such as the Iranian-backed Asaib Ahl al-Haq and Badr Brigade have rushed to support the government. But Sunnis say the militias mistreat people.

“If 10 members of Islamic State come, then they will become a thousand, because all the people of Abu Ghraib will join them,” said an Abu Ghraib resident who works as a laborer and declined to be identified for security reasons.

Many residents hoped that the recent appointment of Haider al-Abadi as prime minister would signal a break from the perceived sectarian policies of his predecessor, Nouri al-Maliki, and perhaps lead to a new level of trust between residents and the army. But that possibility is being hurt by the actions of the Shiite militias, the resident said.

Last week in Khandari — a neighborhood near the notorious Abu Ghraib prison, the center of the prisoner abuse scandal involving U.S. soldiers — residents held a protest against the presence of the militias, whom they accuse of kidnappings and theft.

At the Abu Ghraib market, a young man whispered when he spoke about the militias, so as not to be heard by a nearby soldier. “Nobody can talk, as we are too afraid,” he said. “Sometimes they kidnap people and take a ransom.”

Majidi said he has met with tribal leaders in the area in an attempt to smooth over what he described as “individual acts” by militiamen. But residents say the situation remains difficult.

“They arrest people, and nobody knows where they are taken,” said Talal al-Zowbai, a member of parliament from Abu Ghraib. “This makes so many people want to volunteer with Islamic State to fight the militias.”

The lawmaker argued that the much-touted national guard, a U.S.-supported initiative that would see local Sunni forces protecting Sunni areas, needed to be rolled out urgently to build local support and trust in the state. But the government still has to establish a legal framework for the new security force.

“We live in a constant state of fear” about an attack by the Islamic State, said Umm Jassim, a woman selling beans at the market who used a nickname because of security concerns. “We think it could be just a matter of time before they come.”

Thomas Gibbons-Neff and Karen DeYoung in Washington and Mustafa Salim in Baghdad contributed to this report.