BAGHDAD - Islamic State militants are developing a network of passageways and tunnels in the narrow alleys of west Mosul that will enable them to hide and fight among the civilian population when Iraqi forces launch an attack that is expected any day now.
Residents said the fighters have been opening passages in the walls between houses to allow them to move from block to block undetected, disappear after hit-and-run operations and track government troop movements.
They have also opened sniper holes in buildings overlooking the Tigris river bisecting the city into east and west, they said.
"They opened these holes and threatened us not to close them," one resident told Reuters by telephone, asking not to be identified by name or location because Islamic State executes anyone caught communicating with the outside world.
The militants are essentially under siege in western Mosul, along with an estimated 650,000 civilians, after US-backed forces surrounding the city dislodged them from the east in the first phase of an offensive that concluded four weeks ago.