Isis have taken control of a mountain redoubt in Afghanistan that used to be the fortress of Osama Bin Laden, former leader of al-Qaeda.
Officials and villagers fleeing the area told the New York Times that Isis militants captured the cave complex, in the Nangarhar Province, on Wednesday (14 June) after week-long fighting in the region.
Tora Bora was captured from al-Qaeda in 2001. It subsequently fell under the rule of the Taliban, an Islamic hard-line movement that fights against the government in Kabul and aims to establish a strict version of Sharia law in the country.
Residents claimed that Isis took control of Tora Bora after the Taliban fled, without fighting to maintain control of the area.
However, the Taliban denied the claims and said they were still fighting against Isis, their rival group in the country.
"Fighting is underway in the Tora Bora area between Isis and our mujahedeen," Zabihullah Mujahid, spokesman for the Taliban, said. "It is the front line between our mujahedeen and Isis. No one has advanced in the area."
It is believed that Isis moved to Tora Bora after US forces dropped what was deemed as the biggest non-nuclear bomb ever used in a conflict in the Achin District, Nangarhar, killing at least 36 Isis fighters in April.
Following the seizure of Tora Bora, the Afghani army will begin ground, and air and artillery operations against the militants in the region as soon as possible, officials said.
Afghanistan has been rocked by a string of attacks at the hands of militants that aim to topple the Western-backed government in Kabul.
Last month, Isis claimed responsibility for a truck bomb attack that killed at least 90 people and wounded more than 450 in Kabul.
In April, some 10 Taliban militants disguised as military personnel killed at least 140 soldiers during an attack at a military base in Mazar-i-Sharif, the capital of Balkh Province.
The attack took place just weeks after Isis militants disguised as doctors stormed the country's largest military hospital in Kabul, killing at least 50 people.
The Afghanistan Embassy in London has declined to comment.