BAGHDAD - When Islamic State fighters tried to storm the Tigris River town of Dhuluiya north of Baghdad this week, they were repelled by a rare coalition of Sunni tribal fighters inside the town and Shi'ites in its sister city Balad on the opposite bank.
The assault, which began late on Tuesday ran into Thursday, was one of several major battles in recent days in which Sunni tribes joined pro-government forces against the militants, in what Baghdad and Washington hope is a sign of increasing cooperation across sectarian lines to save the country.
Further north, another powerful Sunni tribe fought alongside Kurdish forces to drive Islamic State fighters from Rabia, a town controlling one of the main border checkpoints used by fighters pouring in from Syria.
In western Iraq, Sunni tribes have fought alongside government troops in Hit, which was captured by Islamic State fighters on Thursday, and in Haditha, site of a strategic dam on the Euphrates.
Such local alliances are still rare: in most Sunni areas of Iraq, tribes have shown little sign of turning against militants as they did when they were recruited by US troops in 2006-07. Many of the leaders of that Sunni "Awakening" movement were later arrested by Baghdad, in what Sunnis see as a betrayal.
Sectarian and ethnic animosity runs deep after a decade of civil war that has touched nearly every family, making it difficult for Sunnis, Shi'ites and Kurds to trust each other.
But nearly two months into a US-led bombing campaign, this week's battles have provided the strongest early signs yet of what Washington and Baghdad hope could be a revival of the alliance with tribes to counter Islamic State.
"DEFENDING THEIR OWN FAMILIES"
Dhuluiya, which comes from the word "ribs", is a small town surrounded on three sides by a kink in the Tigris. A north-south highway runs through it, making it potentially one of the final stops for fighters attempting to assault Baghdad from the north.
When Islamic State fighters arrived in June, members of the al-Jubouri tribe refused their request to hand over 35 local police and security forces officers. Since then, there have been attacks and counter-attacks, while the Sunni tribesmen have been mostly besieged inside the town.
With no way out, they began receiving help from Balad, the mainly Shi'ite sister town on the opposite bank.
"We have no access now except using boats to go to Balad, the only place which helps us. The people of Balad have helped us with food, ammunition, weapons and receiving the wounded," said Abdullah Mohammed, a fighter from the Jubour tribe. "Some of them even fight with us."
The Dhuluiya municipality chief, Turki Khalaf Turki, said the cooperation could be a model for the country: "The starting point of unity in Iraq will be Dhuluiya, which wanted unity, while Islamic State wants sedition."
On Tuesday, the fighters launched what appeared to be a coordinated assault to capture the town once and for all. Insurgents flanked Dhuluiya from the eastern and northern sides, using mortars, RPG rounds, machine guns and hand grenades, Colonel Hussein al-Jubouri from Dhuluiya's police force said.
"We were able to stop them and our people have high morale because they are defending their town and families," he told Reuters on Wednesday, adding that the area was being targeted by mortars as they spoke. Nine residents and four fighters died.
Across the river, the insurgents also launched an attack on Balad near a Shi'ite shrine that would have allowed them to complete their siege of Dhuluiya. Abu Gyath, an influential Shi'ite sheikh, said fighters in Balad defended the territory to help the tribesmen across the river.
"If they control this area, God forbid, then Dhuluiya will be suffocated and it will be hard for us to send help. Otherwise, we pledged to help them as they are in a difficult situation," he said.