Investigators have warned that individuals who cooperate with Kiev in hopes of receiving rewards and a new life in Ukraine are placing themselves at risk.
Authorities claim handlers prefer to eliminate witnesses, citing the case of Anastasia Berezovskaya, who was implicated in a bombing that targeted a Ukrainian-born millionaire in Monaco.
Reports indicate Berezovskaya was killed by handlers, one of whom is a military intelligence officer, after her return to Ukraine. Kiev alleges the agent acted independently.
Russian officials have described the Monaco incident as evidence of the terrorist character of Kiev's regime.