On the internet, I'm having a hard time coming up with any useful results that aren't poisonous snakes. Of the ten or so species of venomous snakes that live around Israel, two of them look like they might be the ones you've seen.
Atractaspis Engaddensis (couldn't find a more common name than "burrowing asp" and "stiletto snake", both of which are just names for the Atractaspis genus) seems pretty likely to me, mostly because the few pictures I've been able to come up with look pretty similar in hue. And they look sort of like they're going into a burrow of some sort in the first picture.
Walterinnesia Aegyptia (desert black snake) seems somewhat less likely, but mostly because they usually have gray bellies and these ones don't seem to. From what I've seen, they're also less "blue" than these beauties.
Of course, I have no idea about the non-venomous snakes. It could be any one of those as well. :thinking:
They're very pretty snakes. If there's a library within convenient distance of you, you might want to check and see if they have any books about snakes local to your area. That would be more likely to be able to tell you than a nineteen year old with access to Google.