Ukraine President Viktor Yanukovych's party claimed victory in an election vote tainted by the jailing of top opposition leader.

Despite a strong showing of pro-Western opposition parties in the proportional portion of the vote, Mr Yanukovych's Party of Regions was likely to retain its parliamentary majority.

With former premier Yulia Tymoshenko in jail and widespread fears of election fraud, the West is paying close attention to the vote in the strategic ex-Soviet state, which lies between Russia and the European Union, and serves as a key conduit for transit of Russian energy supplies to many EU countries.

An election deemed undemocratic by international observers could freeze Kiev's ties with the West and push Ukraine towards Moscow.

An exit poll showed the Party of Regions ahead with some 28.1% of the vote. Ms Tymoshenko's Fatherland party is poised to get about 25% of the proportional vote, while the Udar (Punch) led by world boxing champion Vitali Klitschko is set to get around 15%, according to the survey.

"We believe that this is an indisputable victory of the Party of Regions," Prime Minister Mykola Azarov said after polls closed. "It shows people's trust to the [policy] course that is being pursued."

Opposition parties alleged widespread violations on election day, such as vote-buying and multiple voting and an attack on a candidate who tried to document election violations.

The Committee of Ukrainian Voters confirmed those problems, but said it remains to be seen whether the violations would significantly affect the overall elections results and how fair the vote-tallying will be. Authorities insisted the election was honest.