MOSUL, Iraq (Reuters) - Through the scope of al-Moqdadi al-Saeedi's sniper rifle, Mosul's ruined skyline came into sharp focus, but the Islamic State marksmen he was looking for were nowhere to be seen.
It was just hours since Iraqi forces announced they had raised their flag over the Mosul governorate building on Tuesday following a daring night raid – part of their push to dislodge Islamic State from the city's western half.
But later that day, Islamic State snipers were still active in the area, harassing government troops.
On the top floor of a building nearby, Iraqi snipers were in position, surrounded by spent bullet casings and foam mattresses as they waited for their enemy to show itself.
"Just like we're hiding from them, they're hiding from us," said Saeedi, commander of a sniper unit that is part of the Iraqi Rapid Response division.
As an outnumbered and outgunned Islamic State mount a fierce defence of their last stronghold in Iraq, snipers have been one of their most effective weapons. At times they can pin down advancing Iraqi forces for days.
As snipers themselves, the Iraqi unit understand the Islamic State sniper capability better than most. "The sniper's role is more defensive than offensive," said Saeedi.
The Iraqi snipers say they are having an impact. Earlier on Tuesday, they had killed four Islamic State snipers, according to one of the unit's members, Taif Tala. The rest of the enemy, however, had since changed position and hidden behind some trees.
"They hit that wall a while ago so we figured out which building they were in," said Tala. "We imagine ourselves to be the enemy: if I were the enemy, where would I hide?”
A member of the Iraqi police forces fighting alongside Rapid Response came to tell the snipers that an Islamic State fighter had been sighted. A member of the unit fired a few rounds, filling the room with the smell of gunpowder, but it was not clear if he hit anybody.
Sometimes it proves impossible to deal with an enemy sniper, so the unit calls in heavier weapons or an air strike.
As Iraqi troops move ahead, the sniper unit advances behind them, choosing a position from which to target the enemy without being spotted themselves.
"Eighty-five to 90 percent of it is about hiding," said Saeedi. "Hiding and endurance: they complement each other. Some people can hide but they can't endure: that person cannot be a sniper."
The building in which they were lying up on Tuesday belongs to the Ministry of Justice and appeared not to have been used during Islamic State's two and a half years in the city.
The floors were strewn with ministry files dated before June 2014, when the militants overran Mosul. The papers now bear the boot prints of Iraqi soldiers.
"There are high buildings in front of us," said Tala, explaining that even if an Islamic State sniper climbed on top of them, he could not see his Iraqi adversaries.
Usually the Iraqi snipers would lie on their stomachs because it is easier to stay still that way, and it makes aiming more accurate. But on Tuesday they rested the barrels of their rifles on cupboards they had dragged in front of the window.
Caffeine pills help them stay alert while they wait, Tala said: "Sometimes we don't eat, but you forget your hunger."
Islamic State marksmanship is not to be underestimated. Saeedi showed a picture on his mobile phone of the scope of his rifle, shot straight through by an Islamic State sniper in a previous battle.
"They say snipers are cowardly fighters because they are always behind the troops and they hide," said Abo Ali, a member of the unit. But he added: "We hide, and we kill."
Reporting by Isabel Coles; editing by Giles Elgood