A comedian with no political experience was leading in Ukraine's presidential election on Sunday, an exit poll and partial early results indicated, but was far short of the absolute majority needed to win outright in the first round.

With 11% of the ballots counted, Volodymyr Zelenskiy had more than 29% of the votes, while incumbent President Petro Poroshenko was in a distant second place followed by former Prime Minister Yulia Tymoshenko with about 17% and 14% respectively, the national elections commission said.

The results were closely in line with a major exit poll.

The top two candidates will face off in a presidential runoff on April 21. Final results in Sunday's first round are expected to be announced on Monday morning.

The election was shadowed by allegations of widespread vote buying.

Police said they had received more than 2 100 complaints of violations on voting day alone in addition to hundreds of earlier voting fraud claims, including bribery attempts and removing ballots from polling places.

'First step to a great victory'

Zelenskiy stars in a TV sitcom about a teacher who becomes president after a video of him denouncing corruption goes viral and his supporters hold out hope that he can fight corruption in real life.

"This is only the first step to a great victory," Zelenskiy told reporters after the exit poll was announced.

"Zelenskiy has shown us on the screen what a real president should be like," said voter Tatiana Zinchenko, 30, who cast her ballot for the comedian.

"He showed what the state leader should aspire for - fight corruption by deeds, not words, help the poor, control the oligarchs."

Campaign issues in the country of 42 million included Ukraine's endemic corruption, its struggling economy and a seemingly intractable conflict with Russia-backed separatists in eastern Ukraine that has killed 13 000 people since 2014.

Concern about the election's legitimacy have spiked in recent days after Ukraine's interior minister said his department was "showered" with hundreds of claims that supporters of Poroshenko and Tymoshenko had offered money in exchange for votes.

Like the popular character he plays, Zelenskiy, 41, made corruption a focus of his candidacy. He proposed a lifetime ban on holding public office for anyone convicted of graft.

He also called for direct negotiations with Russia on ending the conflict in eastern Ukraine.

"A new life, a normal life is starting," Zelenskiy said after casting his ballot in Kiev. "A life without corruption, without bribes."

His lack of political experience helped his popularity with voters amid broad disillusionment with the country's political elite.

Poroshenko said "I feel no kind of euphoria" after the exit poll results were announced.

"I critically and soberly understand the signal that society gave today to the acting authorities," he said.

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