Looks chinese to me. This kind of wrought iron "tube" shaped guns ranging in size from pistol/musket calibers to 3-4" bores, were very common weapons/noisemakers from the times of the Ming-dynasty (1368-1644) to the early 1800s. Still in 1860 when the French and British captured the Taku forts near Tientsin (now Tianjin), simple, crude wrought iron guns were found in them. Those guns were very similar, but larger, wrought iron tubes with many reinforcing bands, mounted on simple blocks of wood by iron straps.
The "rounded" shape of the middle band and the shape of the breech and muzzle bands scream "chinese" to me. There are dozens of photos of items like the one you posted on the internet. I'm 99.9% sure it's chinese, but how old is impossible to say, since guns like that were made probably from the late 1300s up to this day. There are also dozens of fake ones everywhere, but they're usually very obvious and yours looks in my opinion old and genuine. But what it exactly is, I'm not sure but I guess the term "thunder mug" would be closest since these seem to be just noisemakers.
Photo of one of the larger "cannon-types" on the Great Wall of China:
http://commons.wikimedia.org/wiki/File:Mutianyu_cannon.JPG
