Neprijatelj (The Enemy), full movie + english subtitles

The story begins a couple of days after the Bosnian war has ended. A group of Serbian soldiers in charge of clearing the fields from mines discover a man sealed inside a factory's basement. The mysterious man says he is "theirs", he doesn't freeze, isn't hungry and only asks for cigarettes. As soon as he is brought along, people start disappearing, and the infighting begins. Who is the mysterious man?