Voting began on Friday in a Russian-controlled part of Ukraine in a referendum that Russia is expected to use to justify the annexation of four regions, with one Ukrainian official reported as saying voting was mandatory.

"Voting has started in the referendum on Zaporizhzhia region becoming a part of Russia as a constituent entity of the Russian Federation! We are coming home! Godspeed, friends!" said

Vladimir Rogov, an official in the Russian-backed administration of that region.