A comedian with no political experience has raced ahead in the first round of Ukraine's presidential election, offering a fresh face to voters fed up with entrenched corruption in a country on the frontline of the West's stand-off with Russia.
With over half of all ballots counted by Monday morning, 41-year-old Volodymyr Zelenskiy, who plays a fictional president in a popular TV series, held a comfortable lead over incumbent President Petro Poroshenko.
The vote has been deemed largely free and fair by the national electoral commission.
A crowded field of 39 candidates has now shrunk to just two, with Zelenskiy and Poroshenko set to go head-to-head in a second round run-off on April 21.
Propelled by his anti-establishment appeal, newcomer Zelenskiy must convince voters he is fit to lead a country that has been at war ever since protests in 2014 ejected a pro-Kremlin government and Russia annexed the Crimean peninsula.
He has been criticised for being an unknown quantity and light on policy detail, and his victory speech on Sunday provided little further insight into what he would do if handed the top job in the second round vote.
Both Zelenskiy and Poroshenko face firmly west, and neither wants to move Ukraine back into Russia's orbit. But investors are also keen to see if the next president would push reforms required to keep the country in an International Monetary Fund bailout program that has supported Ukraine through war, sharp recession and a currency plunge.
With 50.4 per cent of ballots counted by 9am on Monday, Zelenskiy held 30.2 per cent of the vote, the Central Election Commission said.
The result is a powerful challenge to the veteran politician Poroshenko, at 16.6 per cent, and former Prime Minister Yulia Tymoshenko, who trailed in third place with 13.1 per cent.
"I would like to say 'thank you' to all the Ukrainians who did not vote just for fun," Zelenskiy told cheering supporters on Sunday. "It is only the beginning, we will not relax."
In keeping with the laid-back style of his campaign, Zelenskiy's election night venue provided a bar with free alcohol, table football and table tennis games.
Poroshenko called the result a "severe lesson", especially from younger voters, and urged their support in a second round.
"You see changes in the country, but want them to be quicker, deeper and of higher quality. I have understood the motives behind your protest," he said.
Poroshenko sought to portray Zelenskiy as unfit to represent Ukraine abroad, especially when taking on Russian President Vladimir Putin in international talks.
Putin "dreams of a soft, pliant, tender, giggling, inexperienced, weak, ideologically amorphous and politically undecided president of Ukraine. Are we really going to give him that opportunity?" Poroshenko said.
Tymoshenko said at a news conference she might yet challenge the result, adding that her team's exit polling put her in second place.
Poroshenko has fought to integrate the country with the European Union and NATO, while strengthening the military that is fighting Kremlin-backed separatists in Ukraine's east.
