Viktor Yanukovych narrowly won Ukraine's presidential election with 48.95% of the vote, according to preliminary results announced on Wednesday after election authorities finished counting ballots.
Supporters of Prime Minister Yulia Tymoshenko demanded a recount, saying they had evidence of violations at hundreds of polling stations.
With 100% of ballots counted from Sunday's presidential runoff, a Central Election Commission official said Tymoshenko had received 45.47% of the vote, 3.48 points behind Yanukovych.
Tymoshenko, a populist leader of the 2004 "orange revolution" protests that overturned Yanukovych's tainted victory in 2004, has stayed out of the public eye since Sunday after vowing during the campaign to take her supporters to the street if she believed the polls had been rigged.
"We demand that the votes be recounted and the results declared invalid," lawmaker Oleh Lyashko was quoted as saying by the Ukrainian news agency Unian.
Another lawmaker, Andrey Kozhemyakin, said Tymoshenko was preparing an address to the nation to raise the alarm over massive vote rigging in the runoff. He said the Yulia Tymoshenko Bloc had been gathering evidence of irregularities and had lodged complaints about violations at more than 700 polling stations.
"If the election authorities fail to take the decision [to hold a recount], we will go to the courts, the logic is that simple," he said.
The Tymoshenko Bloc and Yanukovych's Party of Regions squabbled over the election results at a parliamentary session earlier on Wednesday.
Lawmaker Anatoly Kynakh of the Party of Regions called the rival group's attempts to challenge the vote "agony."
International monitors have praised the elections, which the United States on Tuesday called a step forward in the former Soviet state's democratic development.
The official results have yet to be announced, although the completed count gave Yanukovych the plurality of votes required to win.
Yanukovych's victory could shift the country's foreign policy back toward Russia and away from the pro-Western course pursued by outgoing President Viktor Yushchenko.
Yushchenko, swept to power by the "orange revolution" that overturned Yanukovych's fraudulent victory in 2004, was eliminated from the first round of the January 17 election.
KIEV, February 10 (RIA Novosti)