ISIS released a video showing the murder of 21 Egyptian Christians in Libya last week.
At the end of the video, the killer warns: "We will conquer Rome, by Allah's permission."
However, rather than be threatened into silence, the Italians kicked back with a series of humorous travel tips, under the hashtag #We_Are_Coming_O_Rome.
#We_Are_Coming_O_Rome of course, all roads lead there, dummies.
Some gave fashion advice from ISIS members wanting to fit in when they arrive in Rome.
#We_Are_Coming_O_Rome When conquering #Rome , please dress up accordingly. #style is all that matters :)
Hey #ISIS! Just packing for Rome. Which pair should I bring? I don't want us to be matching #We_Are_Coming_O_Rome
#We_Are_Coming_O_Rome When in Rome do as the romans do, so please buy some fashionable clothes & swap the jeeps for vespas!
#ISIS #We_Are_Coming_O_Rome Don't put cheese on seafood pasta,don't wear socks with sandals and please leave a nice review on @TripAdvisor
Others gave practical tips for travelling to and around the city.
#We_Are_Coming_O_Rome are you sure?
Don't try coming over the Alps on elephants, the Romans are wise to that trick now. #We_Are_Coming_O_Rome
#We_Are_Coming_O_Rome - don't let #Schettino steer your ships. He has a tendency to get too close to islands...
Others just dispensed practical advice on how to be a good tourist in Rome.
Don't let the man take your photo at the Trevi Fountain; he'll demand 5 euros to return your camera #We_Are_Coming_O_Rome
The main question is: will ISIS be able to afford the tourist menus on offer in central Rome? #We_Are_Coming_O_Rome
Don't fall for the "jump the line!" offers at the Vatican; it's a scam. Just wait your turn like everyone else #We_Are_Coming_O_Rome
#We_Are_Coming_O_Rome Venice is cheaper after carnival, Milan is better for shopping, and don't forget Florence which is also great for food
Did you guys say you wanted to break all the crosses? Might take some time - billions of them in souvenir shops. #We_Are_Coming_O_Rome
Some just wanted to congratulate them on their excellent travel destination.
#We_Are_Coming_O_Rome What a great choice! Lovely weather, beautiful culture and fantastic women. All you don't have.
Sorry, ISIS.
