When Islamic State fighter Marat Nurmagomedov escaped from Syria to Turkey after becoming disillusioned with the militant group, he was unable to return home to Russia for fear of arrest.

Instead, he managed to obtain a passport under another name and flew from Istanbul to Ukraine, whose ability to identify him as a terrorism suspect was hindered by a lack of intelligence sharing between Moscow and Kiev.

The 33-year-old Muslim slipped easily through passport control, aided by the fact that Ukrainian border guards do not use an electronic database that shows the faces of terrorism suspects wanted by Moscow.