Ukraine's defeated presidential election candidate Yulia Tymoshenko was set Tuesday to challenge some results of the bitterly contested polls despite calls on her to ease tension by conceding defeat.

Breaking a day of silence after her defeat to Viktor Yanukovych in Sunday's vote, aides said her party would be contesting some of the results and could then even challenge the overall outcome.

Tymoshenko, known worldwide for her golden hair braid and stylish image, has made no comment since a short address after exit polls.

International observers had praised the election and called for the results to be accepted.

The pro-Russia Yanukovych won by a narrow margin of just over three percent after voters rejected the pro-Western leaders of the Orange Revolution five years ago.

Aides of Tymoshenko -- who had previously vowed to mobilise street protests if she detected fraud -- had twice cancelled press conferences Monday but promised she would speak on Tuesday.

But the deputy head of Tymoshenko's Bloc Yulia Tymoshenko (BYuT) party, Olena Shustik, said a decision to contest some results been taken at a meeting of the faction late Monday.

She said they would first demand a recount of the vote in some polling stations and then take the issue to the courts.

"If the result in the courts is positive, we will question the overall result," she said, according to the Interfax-Ukraine news agency.

"We will do everything to prove that this election was falsified," added BYuT MP Sergiy Sobolev. "We will prepare appeals to the courts in the next days."

Her campaign has long complained of dirty tricks by her opponent but international observers praised the election as impressive and the European Union said it was ready to work with Yanukovych.

Independent Internet newspaper Ukrainskaya Pravda said Tymoshenko had announced at a private meeting of her party late Monday that she would never acknowledge Yanukovych's victory and would challenge the vote in the courts.

"I will never acknowledge the legitimacy of the victory of Yanukovych with such elections," she said according to the site's unnamed source.

However it said a significant part of her Bloc Yulia Tymoshenko (BYuT) was opposing her hard line and seeking to persuade her to acknowledge his victory and go into opposition.

The election result marked a stunning turnaround for Yanukovych, an ex-convict who lost the 2004 elections when the Orange uprising led to the courts finding his side had committed mass vote rigging.

A count from 99.94 percent of polling stations said Yanukovych had 48.94 percent of the vote, while Tymoshenko had 45.48 percent, the central election commission said.

Another 4.4 percent of ballots were cast "against all" in a sign of the disillusionment five years after the Orange Revolution. Some 1.2 percent of ballots were spoiled, the election commission said.

The Orange Revolution swept uncompromisingly pro-Western President Viktor Yushchenko to power and created hopes of a new beginning in the strategic state of 46 million people wedged between Russia and the European Union.

But the dreams crumbled amid political infighting and a dire economic crisis and the new president appears set to take Ukraine on a path to better ties with Russia.

Tymoshenko, a champion of EU integration, was a leader of the Orange Revolution but later fell out bitterly with Yushchenko.

Yanukovych has in the last years emphasised Ukraine's ties with Europe in a bid to shed his reputation as a Kremlin puppet. EU foreign affairs chief Catherine Ashton said the bloc was ready to work with him.

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