Fighting in 50-degree desert heat is bad enough, but add choking exhaust fumes amid the confines of armoured vehicles, and no wonder the soldiers await their daily ice deliveries.

In Tal Abta south of Tal Afar, where Iraqi forces have been engaged in mopping up operations against diehard jihadists of the Islamic State group, a key force is engaged in a vital mission.

Men in T-shirts or military camouflage busy themselves around a special truck amid the constant drone of generators.

At the back of the truck, hosepipe in hand, one member of the team fills eight huge rectangular moulds that are then lowered into an enormous cistern for refrigeration.

The cistern itself holds water that has been salted to accelerate the freezing process as it circulates at high speed.

Salt helps absorb the heat of the water in the moulds which slowly solidifies into ice in an endothermic reaction over five to six hours.

The huge blocks of ice are then trucked to the front line and the thirsty fighters.

Hamid Sallal set up his mobile plant to supply ice to the men of the Hashed al-Shaabi's Ali al-Akbar brigade.

The Hashed is a military coalition of mainly Shiite fighters that was created to help in the Iraqi forces' offensive aimed at eradicating the extremist Sunni IS from the country.

It was established in 2014 following a call by Grand Ayatollah Ali Sistani -- the highest Shiite authority in Iraq -- to counter a sweeping jihadist breakthrough.

- The water boiled -

Everywhere it has fought, the Hashed has been supplied daily by hundreds of vehicles loaded with equipment and food prepared by families in southern Iraq's Shiite holy cities.

"We built this plant by ourselves, with our own hands," says Sallal, dressed in impeccable military fatigues.

He and his men began by taking drinking water to fighters engaged in the long and murderous anti-IS campaign to retake Iraq's second city Mosul, which fell in early July.

But that was before the full searing heat of summer descended on the desert.

When the drinking water began to boil, it was time for a rethink.

"We really needed ice, but it's very expensive," Sallal tells AFP.

New men joined the team and they started making their own.

Every day they supply 288 blocks of ice to the front to cover the brigade's potable water needs.

And every day that means they require 13,000 litres (3,450 gallons) of water to make the ice. It is brought in both by tanker and in bottles.

One member of Sallal's team is a 33-year-old ministry civil servant who took time off to fight as a member of the Hashed.

Ziad Abdel Wahid was wounded, but later rejoined the fight in a different role as an ice-maker.

"By doing this, on the logistics side, I can stay near the front," he says.

Twice a day, at dawn and sunset, he loads pick-up trucks with ice for the trip north to Al-Ayadiah, the last remaining active front line near Tal Afar.

It's exhausting work supplying the brigade.

"They need water and ice if they're to fight and advance," chips in his comrade Aref Ahmed, camouflage cap screwed firmly on to his head.