Here is an answer. The tanks and personnel carriers that Russians are using in Ukraine were confiscated from the Ukrainian bases in Crimea. Unfortunately not all the "separatists" are trained in use of those weapons. So they have to use Russian crews. Locals had a chance to talk to one of those crews and they didn't even try to hide that they were from Russia.
However it seems that Russia is moving its armies to the border again. Russian fighters enter Ukraine's territory up to 4 miles deep providing cover for columns of trucks and tanks for "separatists".
The Ukraine's problems are far from over.
