BEIRUT — An eruption of violence in Iraq is threatening to undo much of what American troops appeared to have accomplished before they withdrew, putting the country’s stability on the line and raising the specter of a new civil war in a region buckling under the strain of the Syrian conflict.
In the western Iraqi province of Anbar, Sunnis are in open revolt against the Shi’ite-dominated government of Prime Minister Nouri al-Maliki. Militants affiliated with Al Qaeda have taken advantage of the turmoil to raise their flag over areas from which they had been driven out by US troops, including Fallujah.
That town, where American forces fought their bloodiest battle since the Vietnam War, is a powerfully symbolic city in the Sunnis’ effort to restore their authority. The Iraqi army, trained and equipped at great expense by the US military before it pulled out in 2011, is struggling to hold its own against what is at once a populist revolt and a militant insurgency.
On Monday, Maliki urged the people of Fallujah to expel Al Qaeda-affiliated militants to avert a full-scale attack by government forces.
Convoys of troops, tanks, and heavy equipment headed toward the town to reinforce troops who were surrounding it.
Instead, however, most residents were trying to leave, packing their possessions into cars and fleeing in any direction they could, just as they did ahead of the US assault on the town in November 2004.
The Obama administration has responded to the crisis by promising to accelerate deliveries of extra weapons to the Iraqi government, including Hellfire missiles and surveillance drones. White House spokesman Jay Carney said US officials are working with the Iraqi government ‘‘to develop a holistic strategy to isolate the Al Qaeda-affiliated groups.’’
Tehran followed suit Monday, saying it was ready to help Iraq battle Al Qaeda by sending military equipment and advisers if Baghdad asks for help, the Associated Press reported. It is unclear whether Baghdad would take the offer, made by General Mohammad Hejazi, the Iranian Army deputy chief of staff. He ruled out the sending of ground troops.
Any direct Iranian help could exacerbate sectarian tensions fueling Iraq’s conflict, as Iraqi Sunnis accuse Tehran of backing what they say are their Shi’ite-led government’s unfair policies against them.
Most analysts and Iraqis say the sectarian violence is rooted in the Maliki administration’s failure to reach out to Sunnis and include them in the decision-making processes of the coalition government, thereby enhancing a sense of Sunni alienation.
‘‘Extra weapons and drones are not going to solve this problem. In fact, they will make it worse, because it will encourage Maliki to believe there is a military solution to this problem, and that is what perpetuates civil wars,’’ said Kenneth Pollack of the Brookings Institution in Washington.
The latest violence erupted after Maliki dispatched troops to disperse a protest site in Anbar’s capital, Ramadi, where Sunnis gathered to air grievances against the government.
The upheaval that followed has evolved into a complicated three-way conflict in which almost all Sunnis have turned against the central government, though some have aligned themselves with militants from the Al Qaeda-linked Islamic State of Iraq and Syria and others have not.
In Ramadi, tribesmen have been fighting the militants and have ousted them from most of the areas they had seized.
But Monday, the advances stalled, and Al Qaeda fighters remained dug in in three neighborhoods on the outskirts of the city, residents said.
The Iraqi army, demoralized and running short of supplies, has proved unable to dislodge the militants, and the ad hoc tribal militias confronting them lack weapons and ammunition, said retired Brigadier General Hassan Dulaimi, a former deputy police chief in Ramadi.
Few support the militants from the Islamic State of Iraq and Syria who have claimed control of the town, a journalist living in Fallujah said. But most don’t dare turn against Al Qaeda, he said, while also having no wish to allow Iraqi security forces back into the town after years of perceived abuses.
Another resident who has participated in protests against the government sought to play down the role of the Al Qaeda-affiliated militants. ‘‘We are all rebels against Maliki,’’ he said. ‘‘Our goal is to liberate the whole of Iraq from Maliki.”
After years of some of the bloodiest fighting of the Iraq war, the United States eventually quelled Al Qaeda in Anbar by arming and funding local tribes against the militants. But Maliki neglected to sustain those relationships and instead embarked on a campaign of persecution of his Sunni opponents.
Since 2011, the war in neighboring Syria has compounded security troubles in Iraq by creating an atmosphere of lawlessness.