Ukrainians are going to the polls to vote in a new president after months of unrest following the ousting of former President Viktor Yanukovych.
There are 18 candidates on the ballot, which is widely seen as a crucial moment to unite the country.
But pro-Russian separatists have disrupted voting in the east, stopping many polling stations from opening and smashing up ballot boxes.
Some 20 people have been killed in fighting in recent days.
Voting in the eastern regions of Donetsk and Luhansk has been seriously disrupted.
There were no polling stations open in Donetsk city, and across the region only seven out of 12 district electoral commissions were operating.
The presidential elections were called after the last elected President, Viktor Yanukovych, was deposed in February amid mass protests against his pro-Russian policies.
Confectionary tycoon Petro Poroshenko, known as the “chocolate king”, is the favourite to win.
By 11:00 local time (08:00 GMT), national turnout stood at 17.5%.