Kabul - For the past couple of weeks Taliban fighters in the eastern province of Nangarhar have been coming under attack from former comrades who have defected to the Islamic State (ISIS).Taliban have been ambushed en route to fight the Afghan army in Sherzad district. Houses of local commanders were burnt down in Spinghar district, and a handful of fighters were beheaded in Achin district.More than three dozen insurgents have been picked off by the rival militants in the past two months, in incidents across at least seven of the province's 21 districts, local tribal elders and government officials told dpa.The Taliban shadow governor for Nangarhar, Mir Ahmad Gul, was shot dead last week in the Pakistani city of Peshawar, two hours east of the Afghan border. A Taliban commander said he was killed by ISIS supporters for leading the offensive against the group.In April, a suicide bomber killed 35 people outside a bank in Jalalabad, the capital of Nangarhar. The attack was allegedly conducted by a former faction of the Taliban that decamped to ISIS last year.The emergence of a new group is just the latest destabilising factor in the province wracked for years by insurgency, drug trafficking, and territorial disputes, said Haji Niyaz, a tribal elder in Khogyani district.Another tribal elder, Noor Mohammad, from the Sherzad district, said many ISIS fighters were taking advantage of the porous border to attack the Taliban faithful and flee to the lawless tribal region of Pakistan.Clashes spreadingMore than 1 000 families have already been displaced by the fighting between the Taliban and ISIS defectors in Achin and Spinghar districts, provincial spokesperson Ahmad Zia Abdulzai said.And the clashes are spreading.In the western province of Farah more than two dozen fighters bearing ISIS colours were killed last month in a clash with the Taliban insurgents over recruitment issues, said Abdul Khairkhwa, a local tribal elder in the Khak-e-Safed district.An Interior Ministry official said on Sunday that there are thought to be fighters aligned with Isis in seven of the 34 Afghan provinces, although they probably number just a few hundred.ISIS is actively recruiting in Afghanistan, Interior Minister Noor ul Haq Uloomi said on Saturday.On Tuesday, the Taliban warned ISIS leader Abu Bakr al-Baghdadi against waging a parallel insurgency in Afghanistan."The jihad in Afghanistan must be conducted under one flag and one leadership against the invading Americans and their servants," said the letter signed by the deputy chief Mullah Akhtar Mohammad Mansoor.The Taliban "on the basis of religious brotherhood asks for your goodwill and we don't want to see interference in our affairs".ISIS followers are Wahabbi-Salafis, while the Taliban are Hanafis, separate versions of Sunni Islam. "Taliban fighters do not target Islamic shrines, while those who decamped to Da'esh [Islamic State] have tried to destroy shrines in the south," a Taliban leader in Kandahar, Abdullah Razaq, told dpa.String of Taliban defectionsTuesday's letter to al-Baghdadi is a departure from the Taliban's usually private approach to settling scores with other militants.Analysts and Taliban supporters say the move was needed to counter a string of defections and fights over turf and finance in recent months."Some of those who are not happy with their commanders or with the leadership in Quetta Shura have left the movement and pledged allegiance to Daesh," said Razaq, referring to the main Pakistan-based council that governs the Taliban.In the north-western province of Faryab, the extremist group Islamic Movement of Uzbekistan, announced it was shifting allegiance to al-Baghdadi, "since the Taliban supreme leader, Mullah Omar, was missing for years". Locally, the group is more powerful than the Taliban.Most insurgent groups active in Afghanistan are under the Taliban umbrella, with Mullah Omar as their Emir-ul Momineen, or commander of the faithful, a quasi-caliph status.Despite their pledges of allegiance, "there is no evidence that local Islamic State supporters have direct links with the group's centre in Iraq and Syria", said Wahid Muzhda, a former Taliban official.Earlier this year, ISIS formally announced the leadership for the Wilayat Khorasan, their branch in Afghanistan-Pakistan, headed by former Pakistani Taliban commander Hafeez Saeed.The 14-member council consisted of all Pakistani insurgent leaders except for two, including the deputy chief, Mullah Abdul Rauf Khadim, a former Afghan Taliban commander and Guantanamo detainee.A Taliban officials said that Khadim had converted to Wahabbism during his detention in Guantanamo. After he was released to Afghanistan in 2007 he was given the role of the shadow governor of Uruzgan province, which he never performed.Last year he started recruiting people to join his Wahabbi group.He was killed in a US drone strike in Helmand in February, which many say was based on information given to Afghan authorities by tribal elders with close relations to the Taliban commanders.