About 40 tunnels were uncovered by Kurdish forces who liberated Sinjar, a town in north-west Iraq this month. The town was under Islamic State rule for over a year.

The tunnels found had sleeping quarters, electricity, sandbags, American-made bomb making tools, medicine and copies of the Koran, as Daily Mail reports.

Shamo Eado, a Sinjar commander from the Iraqi Kurdish fighters known as Peshmerga, said: ‘We found between 30 and 40 tunnels inside Sinjar. It was like a network inside the city.

They used them to “hide from air strikes and have free movement underground as well as to store weapons and explosives. This was their military arsenal” he added.