"practice runs" for even larger-scale attacks planned for Europe and the US.

The official did not clarify whether US or European intelligence had any idea about how the Afghanistan-based jihadists planned to make their way westward, although tens of thousands of Afghan refugees are thought to have entered the EU in recent years amid the migrant crisis which began in 2015.

Daesh's Afghan presence has grown dramatically amid the decline of the terror group's activities in Iraq and Syria. Ajmal Omar, a member of the provincial council of the Nangarhar Province in eastern Afghanistan, estimates that "thousands" of militants have now set up shop in his region.

"Right now in Kunar, the right side of the road is Taliban, the left side is Daesh and the government is in the middle,"he said. "When they began in Afghanistan they were maybe 150 Daesh, but today there are thousands and thousands," he added.

The US and its NATO allies have struggled to gain and keep control over Nangarhar province since the 2001 invasion, with the mountainous province recently becoming home to violent clashes between local Taliban militants and the incoming Daesh terrorists struggling for control.

On Tuesday, Afghan media reported that some 13,300 families were displaced in fighting between the militant groups over the past month and a half, forcing them to settle on the outskirts of the city of Jalalabad. One resident said Daesh had threatened to kill civilians unless they left their homes.

Daesh's Afghan affiliate is known as 'Khorasan Province', with its area of operations said to include Afghanistan, Pakistan