What works for me is jokingly say "Okay you see this space this is call my bubble, you do not enter my bubble, it is off limits, a prohibit zone, now back up slowly you don't wanna trigger a bomb, now keep going back and no bomb or landmine will be trigger, good you are in a safe zone now
" They normally burst laughing when i say that and immediately stop invading my space.
If they still keep invading your space be more direct and explain your discomfort in a respectful way, if they still keep going at it, them you have permission to go Godzilla mode :3