A top official in Ukraine's SBU security service was shot dead in Kyiv broad daylight today by an unknown assassin who immediately fled the scene.

Colonel Ivan Voronych was walking through the Holosiivskyi district of Ukraine's capital city this morning when a man approached him at around 9am local time, according to a report by Ukrainskaya Pravda.

A masked assassin, wearing a black t-shirt and shorts, was seen on CCTV footage springing out from behind a car and blasting the 50-year-old colonel at point-blank range with a pistol as he crossed a road.

He is believed to have fired five shots from a silenced weapon before turning and fleeing.

The CCTV footage clearly shows the assailant sprinting down a road away from the murder scene still clutching his pistol.