Pro-Russia Viktor Yanukovich was Monday on course to become Ukraine's next president after elections punished the West-leaning leaders of the Orange Revolution, but his rival refused to concede defeat.

Yanukovich, the loser in the 2004 elections when the Orange uprising led to the courts annulling his initial victory as fraudulent, declared victory and promised to overcome Ukraine's economic crisis and divisions as president.

But with his margin of victory so far less than three percent after a closer than expected vote, his challenger Prime Minister Yulia Tymoshenko, a champion of EU integration, was showing no sign of conceding.

Yanukovich had 48.6 percent of the vote while Tymoshenko had 45.8 percent, the Central Elections Commission said, based on results from 86.7 percent of polling stations.

Another 4.5 percent of ballots were cast "against all" in Sunday's run-off poll, in a sign of the disillusionment five years after the Orange Revolution. Some 1.2 percent of ballots were spoiled.

Profile: Viktor Yanukovich

The Orange Revolution swept Ukraine's old order from power and created hopes of a new beginning in the strategically-located state of 46 million people wedged between Russia and the European Union.

The results pointed to a stunning comeback for Yanukovich, who had been poised to grab the presidency in 2004 before the Orange uprising swept him aside and brought pro-Western President Viktor Yushchenko to power. Related article: Orange flame dims, but still alight

In a victory speech late Sunday, Yanukovich said the election had opened a "new page" in Ukraine's history and reached out to Tymoshenko supporters after the divisive campaign.

"I will do everything to ensure that citizens of Ukraine -- irrespective of where in the country they live -- feel comfortable and calm in a stable country," he said.

Ukraine is split between a Russian-speaking east, which is Yanukovich's stronghold, and the more nationalist Ukrainian-speaking west that backed Tymoshenko.

He said it was time for Tymoshenko to step down as prime minister and he would appoint a figure who suits him better.

Tymoshenko, who had repeatedly accused the Yanukovich camp of plotting to rig the vote, did not concede defeat as she appeared in front of reporters in a an eye-catching cream dress and trademark golden hair braid. Profile: Yulia Tymoshenko

"So long as the last count is not made, it is impossible to talk about any kind of results," she said. Her right-hand man, Deputy Prime Minister Olexander Turchynov, spoke of "extensive falsifications".

Tymoshenko had previously vowed to mobilise her supporters for street protests if she detected fraud by her rival.

Yanukovich's campaign seemed ready to counter that threat, setting up dozens of tents and sending hundreds of supporters around key official buildings in Kiev over the weekend.

The report of international observers and Tymoshenko's first comments on Monday will be anxiously awaited. Turnout was robust at 69 percent.

The Orange Revolution broke out after Yanukovich was declared the winner of a disputed presidential election in 2004. Thousands poured into the streets to protest vote fraud and Kremlin meddling in the election.

After the protests, Ukraine's supreme court threw out Yanukovich's victory as fraudulent and ordered a re-run, which he lost to Yushchenko. But this time, Yushchenko was eliminated in the first round.

During the election campaign, the media-savvy Tymoshenko made a striking contrast to the uncharismatic Yanukovich, who drew ridicule for his inarticulate speech and was criticised for his criminal record.

Yanukovich was convicted and served prison time for theft and assault in the Soviet era, though his convictions were erased by the courts in 1978.

But with Ukraine's GDP shrinking 15 percent last year due to the economic crisis, many Ukrainians had issues on their minds other than the rhetorical skills of the candidates. Related article: Anger and broken dreams as Ukraine votes

Yanukovich also hired US political consultants to improve his image and emphasised the importance of Ukraine's ties with Europe in a bid to shed his reputation as a Kremlin puppet and gain political redemption.