They are being very liberal with their standard of "war crimes", on old stalinist principle of "findme a man, and i'll find a paragraph". By that logic every single Russian and DPR artilleryman is a war criminal too.
They are also inviting qualification as a terror state equal to ISIL from UK, and by proxy the west, as they are not recognized by them and such obvious violation of Geneva Convention does call for it.
So if they and Russia think the sanctions are so bad they can't get worse, there's bad news for them. In fact its something pro-Ukraine talking heads wildly suggested some time ago, but if Russia and its puppets keep acting this way, they may actually provide enough excuses for that to get political traction.
There is increased speculation that on May 9, 2022, Russian President Vladimir Putin will make a major announcement regarding the invasion of Ukraine, potentially including a formal declaration of war against the people of Ukraine.
www.foxnews.com
And on the other side, they are of course inviting similar treatment from Ukraine.