MOSUL, Iraq (Reuters) - Iraqi special forces are engaged in a punishing and paranoid close-quarters battle against Islamic State in western Mosul as they seek to drive the jihadists out of their last urban bastion in Iraq and deal a major blow to their self-styled caliphate.

A member of the Iraqi Counter-Terrorism Service (CTS) stands next to a burnt car from clashes in the Mansour district of Mosul, Iraq, March 12, 2017. REUTERS/Ari Jalal

Mosul is divided by the Tigris river that runs through it, north to south. Iraqi forces, supported by a U.S.-led coalition, pushed into the western side of the city last month after recapturing the east in an offensive that began late last year.

The urban warfare is now more intense than ever, both because Islamic State fighters have been backed into one half of the city and because the west - home to the old city and city center - is more densely populated.

“The fighting is at much closer quarters. It was street-by-street – now it’s house-by-house,” said Iraqi commando Alaa Shaker, 32, a member of the elite Counter Terrorism Service (CTS).

“We are often literally in the same house, on the roof, and Daesh (Islamic State) is downstairs. Sometimes we drop grenades. If there are civilians, families in the homes, we shout to them to take cover inside a room.”

Seif Rasheed, a 28-year-old CTS medic, said one commando had been killed earlier that day in the same area, shot through the head, and another wounded, shot through the neck and hip.

“Daesh are hiding in homes, opening doors and shooting at troops from just a few meters away,” he said.

The men were speaking as they took a break from the fighting to eat lunch in the courtyard of a western Mosul home, in a neighborhood recaptured from Islamic State the day before.

No one can drop their guard. Shaker paused mid-mouthful, stood up, and brought over two assault rifles that were leaning against the wall, setting them down within arm’s reach.

“Just in case,” he said, miming that a member of the family living inside might otherwise pick one up and turn it on the soldiers eating there. “That hasn’t happened so far, but you have to be careful – we don’t know these people. Islamic State have left supporters and sleeper cells behind.”

SHRAPNEL FLIES

Mosul, in the far north of Iraq, is by far the largest city in the caliphate that Islamic State declared over parts of Iraq and Syria in 2014. The few thousand militants still fighting in the west of the city are overwhelmingly outnumbered by a 100,000-strong array of Iraqi forces, and the head of the CTS said they could be dislodged within weeks.

But the militants’ tactics so far in the Mosul battle - digging in among civilians, and using suicide car bombs, snipers and a network of tunnels to launch waves of attacks - have enabled them to hold out much longer than the government’s initial predictions.

The CTS had stationed armored Humvee vehicles in the street outside the Mosul home, and officers inside studied a map on a mobile phone as their radio constantly crackled with updates.

The frontline of the battle had moved forward, but the neighborhood was not completely secured.

Rasheed peered down a street outside, but cautioned against walking down it. Seconds later, an Islamic State shell slammed down into the road, sending shrapnel fizzing off in all directions. Rasheed moved indoors again.

The impact of explosions from the fighting could be felt.

Another CTS commando, Wamid Salam, calmly identified the blasts as rocket-propelled grenades.

Salam, 33, said he was looking forward to his next leave, to visit his pregnant wife in southern Iraq.

Salam wore new glasses, which were prescribed after the blast from an Islamic State car bomb damaged his vision late last year. “It knocked me to the floor, and I hit my head hard. I also got some shrapnel just below the eye,” he explained.

As he spoke, two armored vehicles drove back from the front line, their bulletproof windows riddled with machine gun fire.

(For a Graphic of battle for Mosul, click tmsnrt.rs/2fd0nGE)