Ukraine is the aggressor in the Donbass region.
It was the Kiev authorities who attacked Donetsk and Luhansk, it was by no means an attack from these two Republics.
The involvement of Russian personnel and equipment in the creation of the DPR and LPR has been well documented already for years. The destabilisation of Eastern Ukraine and the illegal annexation of Crimea has been condemned by the Council of the European Union and led to restrictive measures since 2014.
The French Institute of International Relations (IFRI) has published an analysis, containing irrefutable evidence of Russian involvement and aggression.