Ukraine Prime Minister and presidential candidate Yulia Tymoshenko, who finished second in Sunday's vote, has fought to retain the loyalty of voters angered by what many see as her movement's unkept promises. (Associated Press)

The parliament faction of Ukrainian Prime Minister Yulia Tymoshenko insisted on Tuesday there was widespread fraud in the weekend presidential vote and vowed to take court action.

Tymoshenko trailed opposition leader Viktor Yanukovych by 3.2 per cent with almost all the ballots counted from Sunday's run-off vote, but had yet to concede victory.

"Voting day displayed a cynical violation of Ukrainian law by the teams of Yanukovych, pressure on the electors and a broad arsenal of falsification by the Regions Party," Tymoshenko bloc Deputy Serhiy Sobolev told parliament.

Yanukovych's Party of Regions has rejected calls for another round of voting.

"There will be no third round," Mykola Azarov, deputy head of the Party of Regions, told parliament. "They are dragging us into an unnecessary war."

Election monitor praisies Sunday vote

Tymoshenko rose to international fame after she led mass protests of Yanukovych's victory in the 2004 election, which was widely criticized by international electoral monitors. The protests, dubbed the Orange Revolution, helped sweep her and president Viktor Yushchenko into power with promises of closer ties with the West and democratic reform.

But this year's election was hailed by the Organization for Security and Co-operation in Europe (OSCE) as "professional, transparent and honest."

Joao Soares, head of the observation mission from the OSCE's parliamentary assembly, said the vote was an impressive display of democratic elections.

Tymoshenko told officials with her party that she will "never recognize" the legitimacy of the election, the respected Ukrainskaya Pravda website and Russia's ITAR-Tass news agency reported.

Yanukovych, a former electrician and factory manager, has promoted closer ties to Russia, and has pledged to scrap Ukraine's bid for NATO membership and elevate Russian to the status of a second official language alongside Ukrainian.

Interfax news agency said Russian president Dmitry Medvedev congratulated Yanukovych on Tuesday for his apparent victory.

With files from The Associated Press