YES, they are zombies
In the original zombie mythology, a zombie is a possessed person or corpse, acting under mystical influence, and not necessarily dead (Harry Potter's "Inferi" are a variation of this myth, Buffy the Vampire Slayer features the very original concept).
Zombies as walking living dead brain eater bodies (the one you know) is the modern concept, created by Hollywood, particularly by George Romero.
What Hollywood did was actually separate the meanings of "possessed" and "zombie", but they're originally the same thing.
So yes, what you see in [REC] are actual zombies.