MOSUL • Militants of the Islamic State in Iraq and Syria (ISIS) began reinventing themselves months before US-backed Iraqi forces ended their three-year reign of terror in Mosul, putting aside the dream of a modern-day caliphate and preparing the ground for a different fight.

Intelligence and local officials said that, a few months ago, they noticed a growing stream of commanders and fighters flowing out of the city to the Hamrin mountains in north-east Iraq, which offer hideouts and access to four Iraqi provinces.

Some were intercepted but many evaded security forces and began setting up bases for their new operations. What comes next may be a more complex and daunting challenge for Iraqi security forces.

Intelligence and security officials are bracing themselves for the kind of devastating insurgency Al- Qaeda waged following the 2003 US-led invasion, pushing Iraq into a sectarian civil war which peaked in 2006-2007.

"They are digging in," Mr Lahur Talabany, a top Kurdish counterterrorism official, told Reuters. As part of the United States-led coalition, he is at the forefront of efforts to eliminate ISIS. "I believe we have tougher days coming."

Some Iraqi ISIS fighters have roots dating back to Al-Qaeda's campaign of car and suicide bombs that succeeded in fuelling a sectarian bloodbath in Iraq, a major oil producer and key US ally.

When a US-funded tribal initiative crushed Al-Qaeda, the hardcore regrouped in the desert between Iraq and Syria as ISIS.

REUTERS