Russia don't have biological weapon. But, in case of necesserity, it can be easily created.
I think, your corrupted government, willing to distract your gullible population from the economic problems (and solve their own problems), will start the third season of 'Russian poisoners' with the higher rank victims and biological weapon. For example - strike of genetically modificated Kemerovo fewer in the Parliament. Most of survivers by a starnge councidence are May's supporters, but she blame Russians (baselessely, as usual).