According to Mindaugas Pocius, a Lithuanian historian and author of “The Far Side of the Moon” (Kita mėnulio pusė), an extensive study on the reprisals, over 9,000 civilians — including no fewer than 300 children — were designated as collaborators, court‐martialled and executed by the Forest Brothers.
Of course it should also be recognised that the Soviet Union did genuinely commit ethnic cleansing against quite a large number of groups around this time. It is true simultaneously that there were Nazi collaborators (idk enough about the history to specify this and that group though, I admit).