This m ight be the war crime being ordered:
https://twitter.com/marcorubio/status/1497647958627598337?s=10
Those TOS-1 MLRS with thermobaric warheads (which Russia used in Syria) have reportedly moved into Ukraine toward its second largest city,Kharkiv.
The Russian assault on Kharkiv failed. They have encircled the city, and the assault forces have apparently moved on to reinforce the attack on Kiev.
Some bombardment of besieged Kharkiv has begun, including the destruction of a gas pipeline, which many residents rely on for heat during the Winter.
Some sources have reported that Russia intends to try to induce panic to drive a surrender of the city, and set an example for the rest to capitulate.
Using such weapons against civilian populations would be a clear violation of the laws of war. Violators should be hung as war criminals, including Putin, if he ordered it.