“and removed government officials at gunpoint have ceased to be civilians - they are now rebels”
Correct - They are REBELS, not TERRORISTS.
For the Ukraine government to call them “rebels” means to admit they are shooting their own citizens in a Civil War.
A civil war implies that both sides are capable of sustaining operations at a pretty high level, and are able to deny access to their opposite number. This is just an small-scale armed revolt, where the government is being pretty cautious for both humanitarian and PR reasons. The Syrian conflict is a civil war, because the body count is significant - over 100 a day, and the rebels control large swathes of land through which government units cannot pass without being wiped out. Nothing like that is the case in Ukraine.