“Unknown persons infiltrated into the biggest store of weapons of IS in Tal Afar, killed the guards and set the store on fire,” the source said, Al Sumariya reported.
“This caused a huge blast, which completely burnt the store,” the source, who preferred anonymity, added.
The group, according to the source, has been on high alert, setting up checkpoints and inspecting houses in search for the perpetrators.
On Friday, the group reportedly imposed curfew for unknown reasons and deploying its armed detachments in the town.
The incident comes as Iraqi troops have announced earlier this week that they are concluding arrangements ahead of an imminent invasion on the town.
The Iraqi army’s ninth armored division reportedly reached last week to the boundaries of the town.
An army official was previously quoted as saying that an army division was ordered to leave Mosul toward Tal Afar within preparations to retake the town, which has been set as the next target of operations after victory was declared in Mosul on July 10.