Security services think the area in Bosnia is used for ISIS training camps and could be a base for devastating terror attacks on the West.

Crucially, the location gives IS a key strategic position due to its proximity to the Mediterranean which is used by extremists from Syria, Iraq and North Africa.

At least 12 ISIS fighters trained in the village of Osve have left for Syria in recent months and five are reported to be dead.

Terror expert Dzevad Galijasevic said: “From this village a large number of people went to Syria and are going constantly.