This was announced in a video message by President of Ukraine Volodymyr Zelensky.
"There is information that Russian propagandists are preparing, so to speak, a “mirror response” to the shock of all normal people from what they saw in Bucha. They are going to show the victims of Mariupol killed not by the Russian military, but allegedly killed by the Ukrainian defenders of the city. To do this, invaders collect corpses on the streets and take them out so they can use them somewhere else, in accordance with the scenarios developed by the propagandists. We are dealing with invaders in whom there is nothing human left to justify their murders, they take the dead people as decorations, as a propagandist props. And this is a separate war crime for which each of the propagandists will be held accountable", Zelensky said.