Pretty much the worst kept secret of the entire conflict. Its obvious Putin's strategy is to keep a steady flow of Russian operatives and mercenaries working in eastern Ukraine in order to destabilize the area, all the while demanding the Ukrainian government "stop its assault on their own people the east". If he were truly interested in peace, he would make an all out effort to close the border and withdraw all of his agents back to Russia.
The Ukrainian woman who works for their national security department in the middle of
this video pretty much lays out the entire scheme as it is (which can also be applied to Crimea).
1. Russian operatives come, then recruit pro-Russian locals to take over key government buildings.
2. A distinctly pro-Russian spokesman emerges out obscurity to declare the area wants to join Russia.
3. A referendum at gunpoint is organized in order to fast track a vote to legitimize secession.
The only step that didn't occur in the east compared with Crimea is Putin not accepting the Donbass referendum - mainly because he was bricking it over sectoral sanctions.