The "prime minister" of the self-proclaimed Donetsk People's Republic, Alexander Zakharchenko, said the bodies were discovered in three mass graves located in the village of Nizhniaya Krinka and its surroundings.
In addition, two graves with bodies of members of the Ukrainian military and insurgents were also uncovered, he noted, without giving numbers.
The separatist leader said that some of the bodies had organs missing.
The separatists had announced Wednesday the discovery of the mass graves in the region of Donetsk, prompting Russia to denounce alleged war crimes against civilians committed by the Ukrainian government forces during clashes with pro-Russian militias in eastern Ukraine.
The Russian foreign ministry referred, in particular, to a "mass grave" found by rebels in a mine 60 km from Donetsk with several semi-decomposed bodies in civilian clothes.