Ukraine's ruling "Party of Regions" has claimed victory in weekend elections as early results showed it withstanding the challenge by allies of former Prime Minister Yulia Tymoshenko whose jailing last year sparked global concern.

Ukrainian Prime Minister Mykola Azarov expressed confidence the ruling Regions Party would win the majority of seats in the new parliament after Sunday's vote that the West saw as a huge test for Ukraine's democracy amid the furore caused by the imprisonment of Tymoshenko, international media reported.

While the vote for Tymoshenko's opposition alliance held up, the party of boxing champion Vitali Klitschko fell short of its high expectations while the political baptism of footballer Andriy Shevchenko was set to end in disaster.

Ukrainian President Viktor Yanukovych's Regions Party has 35.6% of the vote against 21.5% for Tymoshenko's opposition party, the central election commission said in a statement based on a 40 % vote count in the proportional system that will determine half the seats in the new parliament.

The ruling party was also on course to win at least 110 seats out of the 225 that are being determined by first-past-the-post single mandate constituencies, an early analysis of the results showed.

"We are expecting that the Regions Party will take the majority in the new parliament," Azarov said. The final turnout was robust at 58%, the central election commission said.

The Communists were polling strongly in third place with 15.1 percent. Klitschko's new UDAR (Punch) party was on 12.8 percent, something of a disappointment given some pre-election opinion polls had placed it in second.

The ultra-nationalist Svoboda (Freedom) party was also due to break the five percent threshold needed to make parliament and was polling 8.0%, the partial results released by the election commission said.

Exit polls had shown a much narrow margin between the Regions Party and Tymoshenko but much of the vote count in more anti-Yanukovych regions still remains to be completed.

Oleksandr Turchynov, deputy leader of Tymoshenko's party, said the voting "showed the people's lack of support" for the government.

His party and other Ukrainian observers said there had been cases of electoral fraud, including the buying of votes. The opposition fears further fraudulent practices will occur during the vote count.

Widespread reports of irregularities at polling stations could be observed according to international media correspondents.