If, as predicted, the vote fails to give any candidate a 50 per cent share of the vote, the run-off between the top two is to be held on February 7.
'Day of calm'
After a campaign that saw the main protagonists trade insults, Saturday was an official "day of calm" with all campaigning banned and posters supposed to be removed from the streets.
|Viktor Yanukovich has reinvented himself as a defender of Ukrainian interests [AFP]
All the main candidates spent the final hours of campaigning on Friday with appearances on Ukrainian political talk shows. Yanukovich also held a glitzy rally in central Kiev attended by top Ukrainian pop stars.
Tymoshenko, her voice hoarse from weeks of campaigning, issued a stern warning against the perils of voting for Yanukovich, saying the country risked becoming "internationally isolated, ruled by oligarch clans and criminals".
Yanukovich replied: "What have the Orange leaders promised and not done over the last five years? They deceived the people."
Yanukovich should win around 40 percent of the vote in the first round and Tymoshenko 23 per cent, according to the latest polls by the Kiev International Institute of Sociology.
But analysts believe the image-conscious prime minister - famed for her traditional hair braid - can still make up ground in the run-off.
The third place is expected to go to businessman Sergiy Tigipko who appears to have made a late surge and is given an outside chance of springing a first round upset.
Yushchenko won the presidency in a re-run election in December 2004 ordered by the courts after tens of thousands took to the streets to accuse Yanukovich of vote-rigging in the original polls that he won.
Yushchenko and Tymoshenko were comrades-in-arms in the Orange Revolution but later became sworn enemies, their relationship poisoned by a perennial power struggle and mutual accusations of criminal wrongdoing.
Since 2004, Yanukovich has sought to reinvent himself with the help of Western PR strategists and to show he is not a servant of the Kremlin but a defender of Ukrainian interests.