Ukraine is beefing up security measures after a series of high-profile

murders in Kyiv as a mysterious unknown group took responsibility for

them on April 17.

Earlier this week, ex-lawmaker Oleh Kalashnikov and journalist-writer Oles Buzina – both known for their pro-Russian leanings – were killed within a 24-hour span. The assassinations followed a chain of mysterious suicides and suspected murders of former allies of ex-President Viktor Yanukovych.