Many people don't get what the supernatural events were about in this movie. It is normal because it contains elements of common themes of ghosts and ufo. However, it deals with neither.
Many of the events of the film makes sense if you understand occult lore of the Middle East surrounding creatures known as the Djinn.
Forget about the Aladdin version of the Djinn. Mythological and occult lore of the Djinn is entirely different. Djinn are said to be of fire that doesn't burn. That is an ancient reference to electricity or magnetism. The word jinn in Arabic has the linguistic meaning of 'invisible' and it also shares the same linguistic root as the word 'mad'.
Let's take a closer look at the movie...
1) The man in the cave is actually a sorcerer. The beings he was communicating with are the djinn. They are invisible to the naked eye, but they registered on the solider's equipment. He provided them water that turned into sand. Djinn in ancient lore are able to materialize things ranging from food to gemstones. However, they eventually turn to dust.
2) Evil tribes of the djinn such as the Beni Ghilan (followers of al-Ghoul) are believed to consume dead human flesh.
3) Ancient records detailing djinn materialization talk about strange sounds like 'buzzing bees' before they appear. In this movie, it is the buzzing sound of a chopper.
4) Magnetic phenomena....there is a little known Arabic text called the Green Island dating back to medieval morocco. This book talks about a man who was kidnapped by the djinn and taken to a magical island. He was returned to his village many years later. He left behind a make-shift map trying to point out where this magical island was. Modern researchers of the story tried to correlate the map with modern geographic data. They discovered that the instructions placed it somewhere in the middle of the Bermuda triangle. The mountain range appears to be another secret home of the djinn and thus seem to reflect strange magnetic phenomena.
5) Weird lights...the same old occult texts when discussing djinn manifestation refer to lights that suddenly appear and shine upon the sorcerer from which emerge strange figures (the djinn).
6) Ending....djinn are reported to have strong telepathic abilities and to be very secretive of their reality. The film's ending is about a man whose brain was scrambled by the djinn after being touched on the forehead by one of them. He got too close and he was neutralized and left behind as an example...
I don't claim to know exactly what the script writer intended with all of those references. I am making an educated guess here based on the similarities (coincidental or intended) between the events of the movie and the ancient mythological narrative.
Check out books such 'Book of Deadly Names' for more info on the djinn.