Ukraine's ruling party is set to win the most votes after the weekend elections, but faces a strong challenge from the jailed ex-prime minister.
The elections for the 450-seat Verkhovna Rada were a huge test for Ukraine's fragile democracy and already overshadowed by the jailing of Tymoshenko, who has now spent over a year in prison for abuse of power while in office.
The Regions Party of her arch-foe, President Viktor Yanukovych, led with 28.1 per cent, a narrow 3.4 percentage points over Tymoshenko's Fatherland alliance with 24.7 per cent, the national exit poll by the Democratic Initiative Foundation found.
Third place on 15.1 per cent was held by the new UDAR (Punch) party of world heavyweight boxing champion Vitali Klitschko, marking its breakthrough on the national political scene but relatively disappointing as some pre-election polls had put it in second place.
The vote shares are difficult to interpret as half the seats on the Rada will be awarded based on a proportional system but the other 225 will be given based on first-past-the-post, single-mandate constituencies.
Further complicating the issue is the probability that five parties will break the five per cent threshold for entering the new parliament and it remains unclear which political alliances they will form.
The elections were the first big vote in Ukraine - wedged between the European Union and Russia and still undecided about whose alliance it values most - since 2004 Orange Revolution co-leader Tymoshenko lost a close presidential ballot to Yanukovych in early 2010.
A defiant Tymoshenko issued a statement from detention calling on Ukraine to oust Yanukovych from power.
'Every one of us has to fight this dictatorship the best they can. Your mass turnout can help overcome ballot rigging,' she said. 'This will be your personal contribution to the removal of Yanukovych from power.'
Tymoshenko, who is now outside of prison receiving treatment in hospital, voted while lying down in bed in the presence of two international observers.
The burly president meanwhile played on his favourite theme: protecting Ukraine from political and economic turbulence.
'I voted for stability and economic growth of our country - for our people to live better,' he said after casting his ballot. - AAP