gang. Why not use a levered catapult which could be improvised/modified on a used truck mounted crane and hurl napalm/LNG cans 100s of metres away? My conclusion is they're more interested in creating publicity/panic than bloodshed;  after all they might not be as inhuman/bloodlusting as many of their enemy claim and they still need to recruit followers for the coming World Jehad One

http://www.shadowedrealm.com/medieval-forum/topic/307-a-brief-history-of-the-catapult/