Ukrainians vote in presidential elections
People in Ukraine have taken part in a presidential election 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 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 Mr Yanukovych was deposed in February amid mass protests against his pro-Russian policies.
At 15:00 (12:00 GMT) national turnout stood at more than 40%, Interfax-Ukraine news agency quoted election authorities as saying.
Confectionary tycoon Petro Poroshenko, known as the "chocolate king", is the favourite to win.
"I am convinced that this election must finally bring peace to Ukraine... stop chaos, stop bandit terror in the east,'' Mr Poroshenko said after casting his ballot in Kiev,
BBC reporters on the ground
"Huge numbers of cameras and reporters from Ukraine and across the world were there too as - with his wife and children beside him - [front-runner Petro Poroshenko] shouted "Glory to Ukraine" and dropped his ballot paper in the box."
Daniel Sandford, Kiev
"Perhaps the most important election in Ukraine since independence in 1991 is simply not going to happen in one of the country's biggest cities."
Mark Lowen, Donetsk
"You can not only feel the tension here, you can easily see it. On our way to the town of Krasnoarmeisk, we found a heavily armed checkpoint of the Ukrainian army. The soldiers are very nervous."
Olga Ivshina, Krasnoarmeisk
Other candidates include former Prime Minister Yulia Tymoshenko, Dmytro Yarosh, leader of the ultra-nationalist Right Sector party, and two prominent politicians from the east, Serhiy Tyhypko and Mykhaylo Dobkin.
If no candidate wins more than 50% of the vote, a second round will take place in June.
Prime Minister Arseniy Yatsenyuk urged people to vote and "defend Ukraine".
On Friday Russian President Vladimir Putin said he would respect the outcome and was prepared to work with whomever was elected president.
Kiev and the West accuse Russia of stoking separatist sentiment - a claim President Putin denies.
In related developments:
- The Organization for Security and Co-operation in Europe (OSCE) has deployed 1,000 observers, but has withdrawn most of its monitors from the Donetsk region over fears for their security
- Separatists have massed outside the Donetsk home of steel magnate Rinat Akhmetov - Ukraine's richest person - who recently accused the rebels of threatening "genocide"
- Italian photojournalist Andrea Rocchelli and his Russian translator Andrey Mironov were killed in clashes between separatist and government forces near Sloviansk on Saturday
- Russian PM Dmitry Medvedev has begun a two-day trip to Crimea - a region Moscow annexed in March - in a visit denounced by Ukraine as a "provocation"
Separatists in Donetsk and Luhansk declared independence after referendums on 11 May, a move not recognised by Kiev nor its Western allies.
The two regions took their cue after the disputed referendum in Crimea that preceded Russia's annexation.
Polling stations closed at 20:00 (17:00 GMT), with definitive results expected on Monday.