Ukraine’s Security Service said Sunday they had killed Russian special service agents suspected of gunning down a fellow officer in Kyiv earlier this week, saying it believed Russia’s Federal Security Service was responsible.

The operation followed the killing of Ukrainian Col Ivan Voronych in broad daylight on Thursday, which sent a chill through Kyiv and marked the latest in an escalating battle between Ukraine’s and Russia’s vast and powerful state intelligence agencies.

Ukrainian Security Service says two Russian FSB agents suspected of killing Colonel Ivan Voronych on July 10 have been "neutralized" in Kyiv Oblast.