Members of Charlie Company of the First Marine Division, 6th Regiment, regroup inside a mosque in Fallujah only hours after taking it. Routed insurgents soon regrouped and rained heavy fire on the mosque, prompting the Marines to leave
Looks like the Mosques are no longer off limits. That's a good thing.
They call them "mosque-forts".
Maybe they only do it after getting intelligence of terrorist networking there. These sound like plain vanilla weapons given the territory.