The Taliban has warned the leader of the Islamic State (IS) group against waging a parallel insurgency in Afghanistan, following several defections and reported clashes with militants loyal to IS.
In a June 16 letter addressed to IS leader Abu Bakr al-Baghdadi, the Taliban insisted that "jihad (holy war) against the Americans and their allies must be conducted under one flag and one leadership."
"The Islamic Emirate (Taliban) does not consider the multiplicity of jihadi ranks beneficial either for jihad or for Muslims," said the letter signed by the Taliban deputy leader Mullah Akhtar Muhammad Mansoor.
"Your decisions made from a distance will result in (the IS) losing support of religious scholars, mujahideen... and in order to defend its achievements the Islamic Emirate will be forced to react," it added.
The letter, published on the Taliban website in Pashto, Urdu, Arabic, and Dari, did not elaborate on its threat.
The Taliban have seen defections in recent months -- with some insurgents apparently adopting the IS flag to rebrand themselves as a more lethal force as NATO troops depart.