A senior Ukrainian security officer was gunned down in a residential parking lot in Kyiv on Thursday before his assailant fled on foot in broad daylight, according to authorities and video footage verified by Reuters.

Kyiv's police force said it was working to identify the shooter and that "measures are being taken to detain him." The slain agent was a colonel in the Security Service of Ukraine (SBU), an official said.

The SBU, a sprawling domestic spy agency that has thousands of staff, said it had opened a criminal investigation into the murder of one of its employees in Kyiv's southern Holosiivskyi district. It did not identify him.