"Moscow claimed, without providing any evidence, that a "mass missile strike" in the eastern city of Kramatorsk had killed more than 600 Ukrainian forces.
But the Ukrainian military says this is untrue.
"This is another piece of Russian propaganda," Serhiy Cherevaty, a spokesman for the Ukrainian army, told the BBC.
Moscow is yet to offer any proof of its claim about the Kramatorsk deaths.
The strikes happened near two school buildings - vocational schools number 28 and 47 - which match with the dormitory numbers provided by Russia. Moscow says the buildings were housing Ukrainian military personnel.
However, there's no visual evidence that shows these two buildings were badly hit or that there has been mass deaths on the scale claimed by Russia.
The local mayor posted images of damaged buildings and said two educational sites, eight apartment blocks and garages were damaged from the explosions.
There were no reported casualties, contrary to the claims from the Kremlin."