Yazidi sex slaves, the loss of Kobani and the struggle to keep infrastructure running in areas captured by Isis are believed to be causing friction among militants in the group.

Recent reports suggest infighting is growing between the ranks of foreign fighters as Isis tries to recover from bombing campaigns against its strongholds in Iraq and Syria.

The Jordanian airforce recently claimed to have degraded Isis’s capabilities by 20 per cent after air strikes against militants were intensified in retaliation for the death of pilot Lieutenant Muath al-Kasaesbeh. Isis is also believed to be suffering financially of late as their supply routes between core territories are damaged.

Sajad Jiyad, Research Fellow and Associate Member at the Iraqi Institute for Economic Reform, said one of the biggest issues to have caused friction between fighters in the past surrounded the decision to keep Yazidi children and women as sex slaves.

Iraq crisis: Yazidi nightmare on Mount Sinjar Show all 15 1 /15 Iraq crisis: Yazidi nightmare on Mount Sinjar Iraq crisis: Yazidi nightmare on Mount Sinjar Iraq crisis Displaced people from the minority Yazidi sect, fleeing violence from forces loyal to the Isis in Sinjar town, walk towards the Syrian border, on the outskirts of Sinjar mountain, near the Syrian border town of Elierbeh of Al-Hasakah Governorate Iraq crisis: Yazidi nightmare on Mount Sinjar Iraq crisis Displaced people from the minority Yazidi sect, fleeing violence from forces loyal to the Isis in Sinjar town, walk towards the Syrian border, on the outskirts of Sinjar mountain, near the Syrian border town of Elierbeh of Al-Hasakah Governorate Iraq crisis: Yazidi nightmare on Mount Sinjar Iraq crisis Displaced Iraqis from the Yazidi community settle at a camp at Derike, Syria. In the camps here, Iraqi refugees have new heroes: Syrian Kurdish fighters who battled militants to carve an escape route to tens of thousands trapped on a mountaintop Iraq crisis: Yazidi nightmare on Mount Sinjar Iraq crisis A pilot based at RAF Marham entering a Tornado GR4 prior to taking off for the reconnaissance mission over Iraq. Several RAF Tornado jets set off from RAF Marham in Norfolk this afternoon to travel to a "pre-position", from where they will fly to northern Iraq to provide improved surveillance of the situation on the ground. The jets, fitted with Litening III targeting and surveillance pods, will be able to fly over the crisis area to provide intelligence and help with the delivery of humanitarian aid Iraq crisis: Yazidi nightmare on Mount Sinjar Iraq crisis A British Royal Air Force (RAF) Tornado GR4 aircraft equipped with the Litening III pod from RAF Marham, eastern England, on their arrival at RAF Akrotiri Cyprus for their reconnaissance mission over Iraq Iraq crisis: Yazidi nightmare on Mount Sinjar Iraq crisis Aid inside a Royal Air Force (RAF) Hercules C130 J aircraft before being airdropped to civilians in Iraq Iraq crisis: Yazidi nightmare on Mount Sinjar Iraq crisis A Royal Air Force (RAF) Hercules C130 J military transport plane at RAF Akrotiri in Cyprus. Britain made a third round of airdrops of supplies to aid refugees stranded on a mountain in northern Iraq, officials said, as Tornado fighters arrived at an RAF base in Cyprus preparing to provide surveillance support for the humanitarian effort Iraq crisis: Yazidi nightmare on Mount Sinjar Iraq crisis Royal Air Force (RAF) Tornado GR4 aircraft, flown in from Britain, stand on the tarmac at RAF Akrotiri in Cyprus Iraq crisis: Yazidi nightmare on Mount Sinjar Iraq crisis A displaced man helps a woman, both from the minority Yazidi sect fleeing violence from forces loyal to the Isis in Sinjar town, as they make their way towards the Syrian border, on the outskirts of Sinjar mountain, near the Syrian border town of Elierbeh of Al-Hasakah Governorate Iraq crisis: Yazidi nightmare on Mount Sinjar Iraq crisis Iraqis including Turkmen, Shabaks, Kurds, Yezidis and Christians, fleeing from assaults of army groups led by Isis, take shelter at Bahirka Camp in Arbil Iraq crisis: Yazidi nightmare on Mount Sinjar Iraq crisis Displaced Iraqis from the Yazidi community look for clothes to wear among items provided by a charity organization at the Nowruz camp in Derike, Syria Iraq crisis: Yazidi nightmare on Mount Sinjar Iraq crisis Displaced Iraqis from the Yazidi community gather for food at the Nowruz camp in Derike, Syria Iraq crisis: Yazidi nightmare on Mount Sinjar Iraq crisis Displaced Iraqis from the Yazidi community gather for food at the Nowruz camp in Derike, Syria Iraq crisis: Yazidi nightmare on Mount Sinjar Iraq crisis Syrian Kurdish Peshmerga fighters take a sick Iraqi Yazidi woman to the clinic at Nowruz camp in Derike, Syria Iraq crisis: Yazidi nightmare on Mount Sinjar Iraq crisis Sick displaced Iraqis from the Yazidi community wait for treatment at a clinic at Nowruz camp in Derike, Syria

Mr Jiyad told The Independent that many supporters had been in denial about the trafficking of kidnapped Yazidi women, who were captured when Isis flooded Mosul and sold off as sex slaves to fighters.

“It shows that not all supporters understand the nature of the organisation,” he said.

Harrowing accounts have since emerged of trafficked women being beaten, raped and even forced to give blood by militants.

A 15-year-old Yazidi girl captured by Isis and forcibly married to a militant in Syria describes her ordeal having escaped (AP)

Isis’s propaganda magazine Dabiq published an article in October justifying the practice of selling women and children. It condemned Yazidis as "pagans" and "infidels” and claimed they were divided among Isis members “according to the Sharia”.

Mr Jiyad said: "Their supporters were in denial until Daesh confirmed it in a magazine; some had said before the revelation that they wouldn’t do such a thing as it was vile, but then were left with egg on their faces."

Tensions are also believed to have risen after Kurdish troops aided by US-led coalition airstrikes retook the Syrian border town of Kobani, which Mr Jiyad says caused some “internal criticism”.

The Syrian town of Kobani has been won back from Isis by Kurdish forces (Reuters)

“I read things on forums where blame was being apportioned, but the higher leadership has kept a lid on it."

Some mid to high level commanders were killed without Isis releasing any "grand press releases", he added, which could indicate that their deaths were the result of an internal feud.

The recent arrest of an Isis cleric who objected to the burning to death of the Jordanian pilot has led to speculation that the group’s increasing brutality could be proving too much even for some of its members.

But Mr Jiyad believes this is unlikely to have proved a divisive issue for core members of the group.

"It may be the case with people close to them or supportive of them, like the cleric, but not its own men," he said. "It is more operational issues that involve local populations and control that are likely the cause of divisions.

Isis fighters parading in a captured Iraqi army vehicle in Mosul, which the group took in June last year (AP)

“Tensions do seem to be on the rise because Daesh has stepped up the arrests and killings of its own men. But it has proved to be incredibly resilient so far under intense pressure so I don’t think the internal divisions will lead to the group's downfall."

Mr Sajad said tensions are more likely to be growing because of the living situations of those still in areas under the group’s self-declared caliphate.

“The poor services are due to a lack of funding, equipment, resources and because the towns under their control are being cut-off from central government. The blame obviously is placed on Daesh by local populations because they are responsible for the upkeep of services. It is only intimidation that keeps the frustration from spilling over."

Meanwhile, Abu Mohammed Hussam, of the Syrian activist group Raqqa is Being Slaughtered Silently, says relationships between Iraqi and Syrian fighters and those arriving from the Gulf are becoming increasingly strained.