Not sure what they could do. It's not like they have the ability to predict where they'll get resistance. It will turn into urban combat similar to Baghdad, Beirut, or Kabul, where it's extremely difficult to maintain unless you just level the city. So the other concern is Putin throwing a tantrum and deciding to bomb it, set fires with their MLRS flame throwers, or other crazy shit.
Ukraine gov reporting that they successfully defended the city through the night attacks.

Hope it's true.