Faced with a cash shortage in its so-called caliphate, ISIS has slashed salaries, asked Raqqa, Syria, residents to pay utility bills in black market American dollars, and is now releasing detainees for a price of $500 a person.

The extremists who once bragged about minting their own currency are having a hard time meeting expenses, thanks to coalition airstrikes and other measures that have eroded millions from their finances since last fall. Having built up loyalty among militants with good salaries and honeymoon and baby bonuses, the group has stopped providing even the smaller perks: free energy drinks and Snickers bars.

Necessities are dwindling in ISIS-controlled urban centres in Syria and Iraq, leading to shortages and widespread inflation.

Electricity rationed, salaries halved

In Raqqa, the group's stronghold in Syria, salaries have been halved since December, electricity is rationed, and prices for basics are spiraling out of reach, according to people exiled from the city.

In this undated photo, ISIS militants hold up their weapons and wave flags on their vehicles in a convoy on a road leading to Iraq, in Raqqa, Syria. The group has had to make cost-cutting measures in recent months. (Associated Press)

"Not just the militants. Any civil servant, from the courts to the schools, they cut their salary by 50 per cent," said a Raqqa activist now living in the Turkish city of Gaziantep, who remains in close contact with his native city.

But that apparently wasn't enough to close the gap for a group that needs money to replace weapons lost in airstrikes and battles, and pays its fighters first and foremost. Those two expenses account for two-thirds of its budget, according to an estimate by Aymenn Jawad al-Tamimi, a researcher with the Middle East Forum who sources ISIS documents,

Within the last two weeks, the extremist group started accepting only dollars for "tax" payments, water and electric bills, according to the Raqqa activist, who asked to be identified by his nom de guerre Abu Ahmad for his safety.

"Everything is paid in dollars," he said.

His account was bolstered by another ex-Raqqa resident, who, like Ahmad, also relies on communications with a network of family and acquaintances still in the city.

Al-Tamimi came across a directive announcing the fighters' salary cuts in Raqqa: "On account of the exceptional circumstances the Islamic State is facing, it has been decided to reduce the salaries that are paid to all mujahedeen by half, and it is not allowed for anyone to be exempted from this decision, whatever his position."

Crippling airstrikes

A Russian-backed Syrian government offensive in Aleppo province, where ISIS controls major towns including Manbij, Jarablus and al-Bab, is also putting pressure on ISIS. Government troops and allied militiamen have advanced toward the town, considered an ISIS bastion, leading many militants to send their families to Raqqa.

'You can sense the frustration, their morale is down.' - Oussama, exiled al-Bab, Syria, resident

An exile from al-Bab said low-level fighters there have begun to grumble. The resident, who asked only that his first name Oussama be used because he still has family in the city, said dozens of residents of al-Bab have fled, ignoring orders from the extremists.

"You can sense the frustration, their morale is down," Oussama said of the fighters.

A former Raqqa resident now living in Beirut said Syrians abroad are sending remittances in dollars to cover skyrocketing prices for vegetables and sugar. One of the other ex-residents, now living in Gaziantep, Turkey, said the road to Mosul was cut off late last year, and prices have risen swiftly — gas is up 25 per cent, meat up nearly 70 per cent, and sugar prices have doubled.

Iraqi government salaries cut

In Iraq, where ISIS has slowly been losing ground over the past year, the Iraqi government in September cut off salaries to government workers within territory controlled by the extremists.

Iraqi officials estimate that ISIS taxed the salaries at rates ranging from 20 to 50 per cent, and analysts and the government now estimate a loss of $10 million minimum each month. Between the loss of that money — and the U.S.-led bombing of cash warehouses — American officials are optimistic that the effect could diminish ISIS's wealth.

Turkish forces fire from the border toward northern Syria from Kilis, Turkey, on Tuesday. Recent airstrikes, particularly from Russian-backed Syrian forces near Aleppo, have cut off some of the main sources of cash and have destroyed weapons of the extreme fundamentalist group. (Halit Onur Sandal/Associated Press)

"We are seeing our efforts having some effect on their financial flows ... On what order of magnitude, I think it's difficult to say," said Lisa Monaco, President Barack Obama's counterterrorism adviser.

In the Iraqi city of Fallujah, fighters who once made $400 a month aren't being paid at all and their food rations have been cut to two meals a day, according to a resident. The account of the resident, who spoke on condition of anonymity for fear of death at the hands of extremists, was supported by that of another family trapped in Fallujah that said inhabitants can only leave the city if they pay $1,000.

ISIS is also allowing Fallujah residents to pay $500 for the release of a detainee, the family in Fallujah told the AP, saying that they believed the new policy was put in place to help the group raise money.

Fines instead of flogging

Mosul residents contacted by AP say ISIS has begun fining citizens who do not adhere to its strict dress code, rather than flogging them as before. The residents say the group has also already confiscated anything valuable, namely cars and other goods that are later resold in Syria.

But the group still controls a vast amount of territory, and they say the Syrian government has made few gains against the extremists themselves.

The Soufan Group, in a Jan. 27 analysis, said the group is looking for alternative funding streams in Libya, where it is under less pressure — and doesn't face airstrikes. And fighters still get their food baskets and free electricity — even if, as one of the Raqqa exiles said, they no longer get Snickers bars and energy drinks.

"I don't think this is fatal for IS," said al-Tamimi. "I still don't see internal revolt as what's going to be the outcome. It's more like a scenario of gradual decay and decline."