Ukrainian opposition leader Viktor Yanukovych is seen at a polling station in Kiev during the presidential vote Sunday. (Efrem Lukatsky/Associated Press)

The pro-Russian opposition leader Viktor Yanukovych is the apparent winner of Ukraine's presidential run-off election, with a lead of almost three per cent by the latest count, which includes 99 per cent of ballots.

Yanukovych declared victory Sunday after exit polls suggested he would win. The latest data from the Central Election Commission shows Yanukovych with 48.7 per cent of votes to Prime Minister Yulia Tymoshenko's 45.7 per cent.

In a sign of widespread dissatisfaction among voters, more than four per cent of ballots were marked "against all."

The Organization for Security and Co-operation in Europe (OSCE) issued a glowing assessment of the election on Monday, hailing it as "professional, transparent and honest."

Joao Soares, head of the observation mission from the OSCE's Parliamentary Assembly, said the vote was an impressive display of democratic elections.

Ukraine's Central Election Commission said late Sunday there was no evidence of large-scale fraud, but it expects that the loser will challenge the results in court.

Tymoshenko postponed a scheduled Monday news conference until Tuesday, leaving open the question of whether she would concede defeat.

Tymoshenko said on Sunday she was refusing to concede, claiming the vote was rigged in Yanukovych's favour, as it was found to be in the 2004 election that prompted the Orange Revolution.

Yanukovych's victory in 2004 was short-lived after Tymoshenko led mass protests that helped sweep her and president Viktor Yushchenko into power.

Yushchenko, who promised pro-democracy reforms and closer ties to the West but was widely seen as a failed president, was eliminated in an earlier round of the latest voting.

Shift back to Russia

A Yanukovych victory would shift Ukraine's government back toward Russia.

Under Yushchenko, Ukraine fostered closer ties with Georgia and made Moscow a frequent target of presidential rhetoric. Tymoshenko as recently as 2007 criticized what she called Russia's imperial ambitions.

Polls showed most voters still supported the economic and political goals of the 2004 revolt, but many were disillusioned with the failure of the leaders to carry out those reforms. The 2008 Russia-Georgia war and a dispute with Russia over energy prices also turned public opinion toward more favourable relations with Moscow, which remains Ukraine's biggest trading partner.

Yanukovych, a former electrician and factory manager, pledged to scrap Ukraine's bid for NATO membership and to elevate Russian to the status of a second official language alongside Ukrainian.

Yanukovych supporters gathered Monday outside the Central Election Commission in the capital, Kiev, in anticipation of protests against the result.

"We've come here to prevent falsification, and we will accomplish this. We are sure of our victory," said one Yanukovych supporter.

Both sides had vowed to rally supporters if they suspected the other side of stealing victory, but Kiev's streets were calm Monday.

With files from The Associated Press