The BBC has some interesting footage (around 50 seconds into the clip) where you can clearly see an armed man in the foreground (so clearly a combatant) and some civilians in the background when a shell (probably a mortar round) drops in the middle of them, killing 3 civilians. (Alternative video by Bloomberg, focusing just on this incident.)
In the same BBC clip you can see Ukrainian military personnel intermingled with civilians, helping them move out of a town. Russia would probably claim the Ukrainians were using the civilians "as shields", something that Russia has already done in this conflict, in similar circumstances.
Where there any such situations in wars that were dissected by the courts such as that for former Yugoslavia (ICTY). What were the outcomes in court?