Prime Minister Viktor Yanukovich's party leads in the Ukrainian general election after the counting of 77 per cent of votes, officials said this afternoon.
The pro-Western opposition earlier claimed victory in an election widely seen as key to ending divisions that have stalled market reform and exacerbated tensions between a nationalist west and Russian-speaking east.
Ukraine's opposition leader Yulia Tymoshenko at a news conference in Kiev
But the Regions Party of Ukrainian Prime Minister Viktor Yanukovich overtook ex-premier Yulia Tymoshenko's bloc as counting progressed today.
The Central Election Commission said the Regions Party's share of the vote stood at 32.3 per cent after yesterday's poll against 32.1 per cent for the Tymoshenko bloc.
A close result would again mean long talks on forming a coalition government. Groups linked to President Viktor Yushchenko, who swept to power in 2004 "Orange Revolution", support Ms Tymoshenko.
But the alliance has been riven by mistrust between Ms Tymoshenko and the President, though the pair formally patched up their differences with a public embrace on television.
The surprise success of a minor centrist party in this election could add further uncertainty. The centrist bloc of former parliament speaker Volodymyr Lytvyn unexpectedly cleared the 3-per cent threshold to win seats in the chamber. The party is willing to could work with either potential governments.
Mr Yanukovich, dismissed the "orange" declaration of victory earlier today as groundless. He said his party would be declared the winner when votes from the industrial, pro-Russian eastern region were counted.
A top Tymoshenko ally said the prime minister's team was conspiring to cheat in its eastern strongholds.
"We will challenge the results in areas where there will be an attempt at vote-rigging," Oleksander Turchinov told reporters.
A presidential aide also expressed concern at the count.
Rigging prompted the 2004 "Orange Revolution" protests that consumed the capital Kiev for weeks in the aftermath of a presidential poll, initially won by Mr Yanukovich. The supreme court annulled the vote and ordered a new poll won by Mr Yushchenko.