It only takes a split second for the expression on the Iraqi soldier's face to transform from relaxed contentment to absolute terror. "Car bomb!"

The scream slices across the otherwise quiet afternoon in Karkukli, a heavily damaged eastern district of Iraq's second city Mosul.

Special operations forces have seized the western half of Karkukli from the Islamic State group, but the eastern half -- like most of Mosul -- remains under IS control.

IS has repeatedly turned to suicide car bombings as part of its defence against Iraqi forces since the operation to retake Mosul was launched four weeks ago.

Elite army troops are finishing their typical lunch of rice and tomato sauce on Monday afternoon when the warning comes through on the Diyala Regiment's walkie-talkie channel.

"Armoured Kia Sportage coming your way. Take cover now!"

The elite Counter-Terrorism Service (CTS) fighters burst into panicked action, shouting at the few civilians on the dusty rubble-strewn road to hide.

Any soldiers carrying weapons lighter than rocket-propelled grenades scramble into abandoned homes, with some kicking through windows to get inside.

"Grab the bazookas!" one unit leader bellows to his forces, several of whom grab anti-tank missiles and take up positions at intersections where they can spot the car.

Drenched in sweat, drivers leap into Humvees and tanks to block off access to the main road.

"Suspicious vehicle is heading north," a voice radios to Lieutenant Abbas of the Diyala Regiment, standing on a rooftop overlooking his unit's forward positions in Karkukli.

The suspected car bomb is about 150 metres (yards) from the CTS's base inside the neighbourhood, he tells AFP.

It is driving slowly along a main thoroughfare dividing the neighbourhood's east and west, likely looking for a route that could bring it closer to CTS forces.

But the troops spent the morning blocking off about a dozen alleyways with tanks and bulldozers, and the Kia Sportage struggles to find a way through.

"It reached our fortified positions and is turning back," the same voice says minutes later.

"Roger. I'll have Hussein set up one (anti-tank missile) for you at the end of the alley," Abbas responds.

- The search is on -

While the imminent danger has subsided, CTS forces remain on high alert -- the search is on.

The gunfire and yelling has died down, and Karkukli's now-deserted streets are eerily quiet as tense CTS soldiers wait for news of the car's location.

As soon as he heard of the suspicious vehicle, Lieutenant Haidar Hussein bounded up the steps to the rooftop of the abandoned three-storey home his unit is using as a base.

The young, clean-shaven soldier is responsible for flying the Mosul Regiment's surveillance drone, which has been instrumental in helping them spot incoming car bombs.

Usually, Hussein locates the booby-trapped cars, which are then targeted by CTS tanks or air strikes from the US-led coalition warplanes circling above.

He isn't so lucky on Monday.

"I put the drone up in the sky as soon as I heard there was a suspicious car, but I can't find it," he says, fixated on the bird's-eye view of Karkukli displayed on the tablet screen in front of him.

The clock is ticking -- the drone's batteries only last 20 minutes and he has no other charged units.

"I'm monitoring this area here, as it's the only way the car can reach us," Hussein explains, pointing to a deserted main road leading into Karkukli from an adjacent industrial zone.

He shakes his head and starts directing the drone back towards his rooftop, sprinkled with broken glass and empty cans of cheap energy drinks guzzled by young fighters.

Minutes later, a pair of grinning CTS soldiers emerge from the staircase. One sets his anti-tank missile in a corner of the rooftop.

"It's gone," the other says, waving his hand to indicate that the car has left their neighbourhood and that they are safe -- for now.