prefix for Flightplan callsigns for the Russian Navy

I am not referring to tactical callsigns, like REACH or Olympus. I want
to know about the prefix they use in filing flight plans in
international air space using ATC. When the Russian Navy flies, do they
use a particular prefix?

When the U.S. Navy flies we see VVxxxx, Marine Corps, I see VMxxxx with
the first 2 x's being the squadron tail numbers I think. The U.S. Air
Force uses Axxxx.

Anyone know the answer?

Thanks.

Sorry for the odd question.


Brian