The Islamic State (IS) militants that overran the majority Kurdish town of Makhmour, northern Iraq in August had help. Local residents say that a number of local Sunni Arabs helped the extremists in the lead up to the attack, supplying them with information on terrain and security forces in the area as well as with food and fuel.

IS are now gone. Kurdish forces retook the town a few days later, and it is once again controlled by local peshmerga militia. Resentment over this betrayal, however, is still strong. On a tattered sofa in courtyard of a base which IS had briefly occupied, one grizzled peshmerga fighter smoked cigarettes in the harsh sunlight and calmly explained to VICE News that he and others would like to expel all Arabs from the region in the most ruthless way possible.

"90 percent of Kurds are now dedicated to the same brutality towards Arabs as they showed to us... We want the destruction of those dogs. We will kill them as soon as the cameras aren't here," he said referring to the influx of media that descended on the region when IS launched a shock offensive into Kurdish territory.

The fighter's resentment towards his Arab neighbours was not new. He said he had battled the troops of former Iraqi autocrat Saddam Hussein in the 1990s and rolled up his sleeves to show scars from where they had tortured him. The latest collaboration with IS, however, was insufferable. "We tolerated them before… but now we will take our revenge… We will kick all Arabs out. A war of ethnic identities is approaching."

It is an extreme sentiment, but one that is symptomatic of a general increase in anti-Arab feeling amongst some Kurds since the rise of IS, leading to demonstrations, social media campaigns and increasingly harsh treatment from members of the security forces.

Of course this is not universal, nor is it official policy, although rumours of tighter employment and residency laws for Arabs circulate. Lawmakers stress that the Kurdistan Regional Government (KRG) embraces all of Iraq's ethnic and religious groups. KRG President Masoud Barzani said that "the terrorists will not be able to damage the relations between the Kurdistan Region of Iraq and its Arab brothers" during an August meeting with French Foreign Minister Laurent Fabius. In another statement, his office said that "Kurdistan Region has been an outstanding model of stability, democracy and peaceful coexistence in Iraq during the last decade," adding that it was "a safe haven" for all Iraqi's ethnic and religious groups, including Arabs, Turkmen, and Christians.

Meanwhile, Makhmour's mayor, Ibrahim Sheikh-Allah, said in an official statement that both Kurdish and Arab residents had returned following the fighting. However, locals recently told VICE News that Arabs were, in fact, being blocked from doing so. One 36-year-old Arab who once ran a shop in the town and gave his name as Abu Omar said he left his home the day that IS attacked and fled to the KRG capital of Erbil to stay with a Kurdish friend. When Kurdish forces recaptured the town and families began to trickle back he was was stopped from joining them by local security forces, known as Asayish, supposedly for his own safety. "I was informed by the Asayish forces that Arabs are not allowed to go back to Makhmour. They told me that the situation is not good enough for the Arabs to go back to Makhmour, since there are people who are hostile to Arabs at the moment."

Resentment is certainly still high. Karwan, a Kurdish resident who declined to give his surname confirmed that there were currently no Arab families in the town, and said that none should be allowed to return. "They were the reason for the fall of Makhmour… they caused too much pain for the people... during these past weeks. He was sceptical even of Arabs who had fled to the KRG. "I don't know about them, but for now there are only Kurds here in Makhmour and we are really living in peace and security…. I think even the innocent ones [Arabs] should not come back for a while since people of Makhmour are really angry."

A member of the Asayish, who declined to give his name, told VICE News that he had orders not to let Arabs back into the town. He speculated that this was partly because Kurds were still resentful, and partly because if IS launched another assault, then the presence of Arabs would be seen by the peshmerga as a risk. "Everyone knows that some Arab families helped IS to take Makhmour and gave them information before they attacked it," he said.

Peshmerga commanders appear to share this concern. Ali Faté, a peshmerga veteran who heads forces on the front just outside the town told VICE News shortly after the town had been retaken that the security situation meant the presence of Arabs was a danger. "You can't say that all Arabs are cooperating with IS, but it's a state of war..." he said, trailing off.

This suspicion is widespread. When VICE News was stopped at a checkpoint on the way into Kurdish territory from the disputed northern Iraqi town of Kirkuk, a peshmergera fighter looked inside the vehicle, asked "Any Arabs?" and when told there wasn't, waved it on with no further questions.

Arabs report being held up far longer at checkpoints and treated with hostility by those manning them. Worries of IS spies has meant that entire families were turned away at border crossings while attempting to seek refuge in Iraqi Kurdistan. A source close to senior peshmerga commanders at the frontline between Erbil and IS-held Mosul who spoke on the condition of anonymity told VICE News that a number of internally displaced Arab Iraqis, including young children, had been refused entry to the KRG on the suspicion that they were IS informants. "They often use children to do their spying for them, we have caught several," he said.

Meanwhile, anti-Arab rhetoric is mounting amongst civilians. As well as allegations of IS sympathies, the vast influx of refugees fleeing the fighting has pushed up housing and commodity prices. KRG minister for social affairs Muhammed Kader Hawdeyani said in July that crime too had risen as a result of the new arrivals, according to local BasNews.

In response, a now removed Facebook page calling for Arabs to be expelled from Iraqi Kurdistan quickly racked up thousands of likes, while a number of protests with the same demands were held, including one in Erbil which reportedly involved makeshift checkpoints looking for Arabs. Cars with Mosul license plates have been vandalised whilst some business have apparently refused Arab customers or charged them more.

The reason for this current enmity may be new, but as the peshmerga fighter alluded to, there is longstanding Kurdish resentment against Arabs. This is partly due to their brutal treatment under Hussein's rule, which saw thousands killed and the enactment of an "Arabization policy" that forcibly resettled thousands of Arabs in Kurdish regions and evicted Kurds from their homes.

Security was also stepped up after a September 2013 attack on security forces in Erbil, and local media reported that Arabs — particularly single men — were turned away at borders into Iraqi Kurdistan.

Today, there are more positive signs too. Anti-Arab demonstrations have been blocked by authorities, whilst in a Kurdish-run IDP camp on the outskirts of Erbil those who had fled IS — Arabs and members of Iraq's minority groups alike — praised the treatment they had received from local Kurds.

Nevertheless, Kurdistan has long prided itself on being more tolerant, prosperous and safer than the rest of Iraq. It will likely to continue to be so, but if recent trends continue, this history of tolerance, at least, may be at risk.

Additional reporting by __Mohammed Rasool