I can tell you this is known to be true here in Bosnia. I know a couple guys who've been out hiking and been "tracked" by wolf packs (consisting of 2-4 animals that these guys saw). These guys are trustworthy friends and not into drama and hype (though i live in a different part now, it's still usually on my mind when i'm out). Wolves have been known to prey on the "wild" horses in Western Bosnia/Hercegovina as well as preying on sheep/goats in some of the more remote parts in north eastern Bosnia.
I'd expect Member Name "Rinos" to chime in as he lives in Split, Croatia (i used to visit there monthly - beautiful city BTW). Incidently, Croatia used to be part of Former Yugoslavia (as was Bosnia, etc.....).
The Balkan's have a couple shepherd dog breeds that were bred specifically to guard against predation like this - the Sar (pronounced SHAR) Planinatz and the Tornjak - both big!