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.

SBU officer Ivan Voronych was shot dead in Kyiv on Thursday morning in what authorities told CNN was an apparent assassination.

The suspects – a man and a woman – tried to “lay low” after the shooting, the SBU said in a statement Sunday.

However, SBU and National Police officers established their whereabouts in the Kyiv region, the statement added.

The head of the SBU, Vasyl Malyuk, said; “As a result of covert investigative and active counterintelligence measures, the enemy’s lair was discovered.”