This has been reported, off and on, for several months now.
That was always Putin’s obvious strategy. To have the “green men” stir up trouble and if the separatists look like they are losing too bad, roll Russian armor for a “humanitarian peace keeping mission”. It’s hard to peer through the propaganda and see how successful the Ukrainians are really being but the likelihood seems to be that at some point they will make Putin decide whether he and his “peacekeepers” will back the separatists with armor.