Ukraine's defeated presidential candidate Yulia Tymoshenko will challenge the results of the bitterly contested election, aides said yesterday, intensifying fears the country is heading for political turmoil.

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

Ms Tymoshenko, 49, famed for her golden hair braid, stylish image and political tenacity, has disappeared from public view since the election results were published and has made no comment since a short address after exit polls. Pressure has grown on Ms Tymoshenko to concede defeat after internationalobservers and the West praised the election as an impressive display of democracy in the ex-Soviet state.

The pro-Russia Mr Yanukovych, 59, won by a narrow margin of just over 3.5 per cent after voters repudiated the pro-Western leaders of the Orange Revolution five years ago in which Ms Tymoshenko had been a leading protagonist.

Ms Tymoshenko's team had twice cancelled press conferences Monday and promised she would speak yesterday. But there was still no sign of her breaking cover and the Interfax-Ukraine news agency said she may issue a statement instead.

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

She said they would first demand a recount of the vote in some areas 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 Interfax-Ukraine.

"We will do everything to prove that this election was falsified," added BYuT lawmaker Sergiy Sobolev.