An FSB agent linked to a hit squad ordered to kill a top Vladimir Putin foe has vanished and may have been assassinated, according to media reports.
Journalists who unmasked the plot to murder Alexei Navalny by sprinkling his underwear with Novichok now fear for the life of their key source.
FSB operative Konstantin Kudryavtsev, who in his early 40s, was duped into disclosing full details of the sinister plot in a phone call to Navalny who posed as a senior Russian security official.
