President Viktor Yanukovych's ruling Regions Party will retain control of the country, with early results indicating he has the greatest support after Sunday's vote.
Early results from Sunday's election show President Viktor Yanukovych's Regions Party will secure a parliamentary majority after winning 36.6 percent of voter support.
Results showed opposition party Fatherland, led by former prime minister Yulia Tymoshenko, who is currently serving a prison sentence for abuse of office, finished at 21 percent.
The results from the election of the 450-seat parliament, published by the central election commission, are based on 30 percent of the ballots.
Ukrainian boxing champion Vitali Klitschko conceded on Sunday evening (local time) that he had expected a better outcome than the 12.6 percent with which he finished.
The reigning heavy-weight world champion told local television station 1+1 he would ensure election officials carefully counted each of the votes awarded to his liberal UDAR party.
"We are doing and will continue doing all we can to make sure that we do not lose a single one of our votes," Klitschko said.
"I had said that we had tremendous potential," the boxer added. "We must still analyze everything, why we could have won more votes, but failed to do so."
The Ukrainian nationalist Freedom party was the election's biggest surprise, finishing with 7.6 percent of the vote, guaranteeing that it will win more than one seat in parliament for the first time.
Former PM Tymoshenko appeals to voters
Tymoshenko said in a statement released via her legal team that the ballot had been neither fair, nor democratic.
"Only blind or deaf people can call these elections fair, no matter who wins them," she said, appealing to voters to expel the ruling Regions Ukraine party from office.
Representatives from the Organization for Cooperation and Security in Europe (OSCE) watched on as Tymoshenko filled out her ballot from the prison's medical facility, where she is receiving treatment for back problems.
Some 3,700 election monitors from foreign governments and international organizations were in Ukraine to scrutinize the vote, according to the country's Central Election Committee.
Voting irregularities were reported, including voters being handed pens with disappearing ink, the election commission receiving unmarked voting papers after the ballot had officially opened, and intimidation of election observers.
In a statement aired on local television channel Inter, Prime Minister Mykola Azarov rejected the irregularity calls. "We have shown that we have conducted these elections on a fairly high level," he said.
jlw,dr/jr (dpa, AP, AFP, Reuters)