Their work remains incredibly dangerous as the Islamic State group has shut down mobile phone networks and regularly kills suspected government collaborators. However, their intelligence could prove invaluable as the U.S.-led coalition steps up airstrikes around Mosul, Iraq’s second-largest city, to disrupt Islamic State group supply lines ahead of an expected operation later this year to take back the city from militants

“Those patriotic groups, some operate from inside the city of Mosul and others from the areas surrounding it, are now giving us information about the military preparations being made by Islamic State group in order to face any attack by government forces to retake the city,” al-Zamili told the AP.

The Islamic State group captured Mosul in August during its blitz across northern Iraq. The militants now hold about a third of both Iraq and neighboring Syria in its self-declared caliphate.

Many soldiers and police officers dropped their weapons and fled during the extremists’ initial offensive. Now, however, some have begun spying on behalf of the Iraqi government, al-Zamili said.