JALALABAD, Afghanistan (AP) – Rahman Wali’s younger brother was one of 10 Afghan men forced by Islamic State (IS) militants to kneel over bombs buried in the soil in a lush green valley in eastern Nangarhar province. The extremists then detonated the bombs, turning the pastoral countryside into a scene of horror.

The August killings were recorded on camera and posted on social media like so many IS atrocities across the Mideast – reflecting how the Islamic State is exporting its particular brand of cruelty as the group seeks to enlarge its footprint in Afghanistan.

It was through the macabre video that 44-year-old Wali learned the fate of his brother, Rahman Gul, an imam in their remote Shinwar district bordering Pakistan. Gul had been kidnapped weeks earlier, together with his wife and six children who were quickly set free.

After his brother’s death, Wali and his family fled to the provincial capital of Jalalabad, seeking refuge in a makeshift camp with thousands of others who left their homes in the valleys hugging the border to escape what is turning out to be an increasingly vicious war for control of the region between the Taliban and fighters of Afghanistan’s IS affiliate.

Reports of an IS presence in Afghanistan first emerged early this year in southern Helmand province, where recruiters believed to have links to the IS leadership in Syria were killed by a US drone strike in February.

In the summer, extremists pledging allegiance to IS also surfaced in Nangarhar, where they challenged the Taliban in border clashes. After see-sawing between the two groups, four districts – Achin, Nazyan, Bati Kot and Spin Gar – fell under IS control, according to General John F Campbell, the US commander of American and NATO forces in Afghanistan.

Campbell told

The Associated Press in an interview last week that IS loyalists in Afghanistan are now trying to consolidate links to the mothership – the so-called “caliphate” proclaimed on territory IS seized in Syria and Iraq after its blitz there in the summer of 2014.

For the present, IS ambitions for Afghanistan seem focused on setting up what it calls “Khorasan Province”, taking the name of an ancient province of the Persian Empire that included territories in today’s Afghanistan, Iran and some Central Asian states. It parallels names for affiliates elsewhere, such as the IS branch in Egypt’s Sinai Peninsula, which is known as “Sinai Province”.

“I think ISIL is really trying to establish a base in Nangarhar … and establish Jalalabad as the base of the Khorasan Province,” Campbell said, using an alternative acronym for IS.

Several residents who fled the four Nangarhar districts say IS’s “reign of terror” there includes extortions, evictions, arbitrary imprisonment and forced marriage for young women. Beheadings and killings with “buried bombs” – such as the gruesome slaying of Wali’s brother – are filmed and posted on social media to instil fear, they said. Some spoke on condition of anonymity, fearing reprisals for relatives back in the districts.

Mimicking IS’s media outreach in Syria and Iraq, the Afghan branch also set up a radio station in Nangarhar,

Radio Caliphate, broadcasting at least one hour a day to attract young Afghan men disenchanted by dim job prospects in a war-torn country with an overall 24 per cent unemployment rate. The joblessness is even higher among youths targeted in the IS recruitment drive.

Meanwhile, the Afghan Government forces, busy fighting the Taliban elsewhere, left the two militant groups to battle it out.

And battle they did. Hundreds of Taliban fighters – disillusioned with the 14-year war to overthrow the Kabul government – switched allegiance to IS.

Though estimates say that IS fighters number a few thousand nationwide, they are still far outnumbered by the Taliban, who have anywhere between 20,000 and 30,000 in their ranks, according to Afghan political analyst Waheed Muzhdah, who worked in the Taliban foreign ministry during their 1996-2001 rule.

Still, many admit the IS Afghan branch could pose a serious threat to the unstable nation.

In a report released last week, the Pentagon referred to the “Islamic State of Iraq and the Levant – Khorasan Province” as an “emergent competitor to other violent extremist groups that have traditionally operated in Afghanistan”.

“This may result in increased violence among the various extremist groups in 2016,” the December 16 report said.

Campbell said some foreign IS fighters have joined the Afghans from Iraq and Syria. Former residents said they spotted gunmen from Pakistan and Uzbekistan, as well as Arabic speakers flush with money and apparently better armed than the Taliban.