"Gregory Waters, a research analyst with the Counter Extremism Project, told Metro.co.uk: ‘It’s nothing like the oil trade Isis had when it was controlling territory, but they don’t have the expenses they had before.

‘All they need now is supplies for their cells and to pay the smugglers.

‘It’s an easy and lucrative operation. It also serves a second purpose in that by killing shepherds and stealing sheep there are more internally displaced people, which means more smuggling routes and informal crossings.

‘This makes it easier for Isis fighters to infiltrate areas as they can hide among strangers moving from place to place.’"