So far I got:
- Solaris
- Ikari XB-1
- Come & See
Also:
- Viy
- The Sacrifice
- Satana (1991)
Plus a bunch of the ones mentioned in the comments now.
Kin-Dza-Dza , Mad Max Soviet-style, a satirical dystopia.
Gentlemen of Fortune, a comedy-drama about petty criminals trying to fit in society.
The Meeting Place Cannot Be Changed, a hardboiled crime thriller set in post-WWII Moscow.
Sideburns, a Perestroika-era prophetic movie predicting the rise of Neo-Nazis in Russia.