MOSUL, Iraq (Reuters) - As Iraqi government forces advanced towards his eastern Mosul neighborhood in November, a group of Islamic State militants stormed Abu Rami’s home, put a gun to his head and told him and his family to get out immediately.

The militants, including a local man whose name he knew, brought with them a bearded comrade clutching a sniper rifle whom Abu Rami suspects was Russian or Chechen. The foreigner took up position in a rooftop chicken coop.

When Abu Rami returned 11 days later, the fighting had ended and the militants had slipped away, but his two-storey house was destroyed by an air strike. His family is now distributed among relatives and friends across the city.

“Destruction occurs in a few moments, but rebuilding takes time,” he said outside the rubble of his home where men huddled around a well to collect water because pipes have been damaged.

The Mosul campaign, involving a 100,000-strong alliance of Iraqi government troops and militarized police, Kurdish security forces and mainly Shi’ite Muslim militiamen, is the most complex battle in Iraq since the U.S.-led invasion in 2003.

With nearly all of eastern Mosul under government control three months into the U.S.-backed offensive, most residents have stayed in the city, complicating the task of the military which must fight among civilians in built-up areas against an enemy that has targeted non-combatants and hidden among them.

Residents told Reuters during a visit to the Muharibeen district on Friday how the battle played out for them, describing scenes likely repeated in one form or another across the city.

The militants hung curtains across roadways to try to obscure the view of Iraqi army marksmen as they dashed from houses to pray in a tan-colored mosque where they also posted a sniper in the minaret, Abu Rami said.

They kept a car packed with explosives parked opposite his house for more than a week. When they deployed it to a main street, an army tank shelled it, destroying an adjacent building.

DIVISION OF LABOR

When it launched the offensive in October, the Iraqi government hoped to retake Mosul - Islamic State’s last major stronghold in the country and the largest urban center anywhere in its self-styled caliphate spanning neighboring Syria - by the end of 2016.

But Prime Minister Haider al-Abadi said in December it could now take another three months to drive the militants out.

Commanders have said the presence of up to 1.5 million residents and attempts to minimize destruction to homes and key infrastructure has slowed their troops’ advance, though hundreds of civilians have already been killed and many areas heavily damaged.

Abu Rami, a 54-year-old former government employee, described a division of labor among Islamic State militants at the frontlines: a group that plants explosives, one that has snipers and another that serves as local guides.

The snipers are usually Russians, Chechens or Afghans, he said. The Iraqis, many from Mosul and the nearby city of Tel Afar, ride around on motorcycles telling them where to take up positions.

Abu Rami said he was surprised when the fair-skinned sniper who posted up in his house spoke to him in broken Arabic, saying: “For the sake of Allah, get out.”

“They do not know the area so the motorcycle guides the suicide car bomb (to its target) and tells the fighters, ‘You go here, you go there. Go detonate here’”, he said.

U.S. Army Lieutenant-General Steve Townsend, commander of the international coalition backing Iraqi forces, told Reuters last week that Islamic State’s local leadership had proven effective without a hierarchical chain of command.

But he said separate cells fighting in different neighborhoods appeared increasingly unable to coordinate across different areas it controlled inside the city.

Another U.S. military official said fighters the coalition observes moving skilfully across Mosul’s urban terrain usually turn out to be foreigners.

According to another Muharibeen resident, who asked not to be named, Islamic State will shoot from a position for several minutes until the military identifies the location. The militants often escape to another house through holes previously knocked through outer walls.

“Then there is bombardment to destroy the house, to destroy the sniper position,” he said. “But the sniper will pop up again here or there.”