Pro-Russian rebels are holding an election to set up a separatist leadership in eastern Ukraine, but the poll has been denounced by the west as “illegitimate”.
Both the US and European Union have criticised the poll. Ukranian president Petro Poroshenko has called on Russia not to recognise the result.
Parts of eastern Ukraine have been in the control of pro-Russian rebels since the former Moscow-backed Ukrainian president Viktor Yanukovych was ousted by protesters in February.
In Donetsk and Luhansk regions there have been months of heavy fighting between pro-Russian rebels and the Ukranian military. At least 4,000 people are thought to have died, with thousands more leaving their homes.
Kiev says the vote violates a series of agreements known as the Minsk protocol that underpins a ceasefire between the rebels and Kiev.
Hours before the vote began, loud shelling was heard north of Donetsk.
Ukraine’s military said three of its soldiers had been killed in the past 24 hours, two of them by an explosion at a check point near the city of Mariupol, which is under Ukrainian control.
Alexander Zakharchenko, the current rebel prime minister whose campaign advertisements are plastered across the rebel-held city of Donetsk, seems almost certain to win the vote for the leadership of the self-proclaimed Donetsk People’s Republic.
Russia has given its support to the polls, with Foreign Minister Sergei Lavrov stating that Moscow would recognise the vote.
On Friday, German Chancellor Angela Merkel told Russian President Vladimir Putin the election was illegitimate and would not be recognised by Europe.