KIEV (AFP) - More than 36 million people are eligible to vote in Ukraine's presidential election which the West hopes will help end a crisis that has brought the country to the brink of collapse.
Here are 5 things about the vote.
1. Sixth and most crucial
This is the sixth vote since Ukraine became independent with the disintegration of the Soviet Union in 1991, and arguably its most crucial.
The election was called by the new leadership that swept to power after the ousting of pro-Moscow president Viktor Yanukovych. He fled in February after months of often bloody protests against his rule and in favour of closer ties with the European Union.
The names of 21 candidates are on the ballot papers, but three have since withdrawn.
The frontrunner is billionaire "chocolate king" Petro Poroshenko with over 45 percent support in opinion polls, ahead of the deeply divisive former darling of the 2004 Orange Revolution, Yulia Tymoshenko, on 7.5 percent.
The other hopefuls are a mixed bag of politicians, including pro-Russians and ultranationalists, but none are tipped to win more than seven percent.
And despite the radically different political scene that has emerged since the so-called Maidan protests in Kiev, there are no fresh faces among the leading candidates.
No minimum turnout is required to validate the outcome but if no candidate wins more than 50 percent, a second round run-off will be held June 15.
The figure of 36 million includes voters in the rebel-held east and Ukraine's Black Sea region of Crimea which was seized by Russia in March.
In addition to the presidential ballot, voters will be choosing new mayors in several major cites including Kiev - where the favourite is champion boxer turned opposition leader Vitali Klitschko.
4. Polling stations
There are almost 33,600 polling stations nationwide but election officials have warned they face problems in the insurgent strongholds of Donetsk and Lugansk which declared themselves independent republics after disputed May 11 referendums.
Ukrainian authorities have also set up stations in the south to enable people in Crimea to vote, but it is not clear whether or how they will cross from what Russia now considers its territory.
The Organisation for Security and Cooperation in Europe has about 1,000 observers to monitor the vote.
Polling stations will open at 0500 GMT (1pm Singapore time) and close at 1700 GMT.
Three independent institutions will issue exit polls immediately after the close, with results expected to be announced from 2100 GMT.
One of the tasks of the new president, who will be elected to a five-year term, will be to set the date for elections for the 450-seat parliament.