* Comedian in lead with 30% of votes
* Appeals to voters fed up with corruption, status quo
* No candidate expected to win outright
* Incumbent Poroshenko staunchly pro-West

A comedian with no political experience raced ahead in the first round of Ukraine's presidential election on Sunday, offering a fresh face to voters fed up with entrenched corruption in a country on the frontline of the West's standoff 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 in a vote 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 programme that has supported Ukraine through war, sharp recession and a currency plunge.

With 50.4 percent of ballots counted by 09:00 (06:00 GMT) on Monday, Zelenskiy held 30.2 percent of the vote, the Central Election Commission said.

The result is a powerful challenge to the veteran politician Poroshenko, at 16.6 percent, and former Prime Minister Yulia Tymoshenko, who trailed in third place with 13.1 percent.

LAID-BACK STYLE

‘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.

Poroshenko said the vote was free and met international standards. Tymoshenko said at a news conference she might yet challenge the result, adding that her team's exit polling put her in second place.

Stuart Culverhouse, head of sovereign and fixed-income research at investment bank Exotix, said Zelenskiy had tried to present himself more professionally by meeting business leaders and talking of orthodox economic policies.

‘That said, if the exit polls are confirmed in the official vote count, we would expect Zelenskiy to be put under greater pressure in the run-up to the second round to flesh out his policy agenda,’ he said.

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.

Voting was a snapshot of Ukraine's recent history. Soldiers lined up to vote in makeshift polling stations in the east.

Voters formed long lines outside polling stations in neighbouring EU member Poland, where between one and two million Ukrainians have moved, many in search of jobs and higher wages.

Pushing the use of the Ukrainian language and instrumental in establishing a new independent Orthodox church, confectionary magnate Poroshenko, 53, has cast himself as the man to prevent Ukraine again becoming a Russian vassal state.

But reforms to keep foreign aid flowing have been patchy. Conflict in the eastern Donbass region has killed 13,000 people in five years and rumbles on despite Poroshenko's promise to end it within weeks. Frustration over low living standards and pervasive corruption has left the door open for Zelenskiy.

The majority of voters in separatist-held eastern Ukraine and Crimea were unlikely to take part in the election as they needed to undergo a special registration process on Ukraine-controlled territory.

ANTI-ESTABLISHMENT

But Crimean residents who kept Ukrainian citizenship after the Russian annexation crossed the land border to mainland Ukraine, from where buses took them to polling stations.

Just 9 percent of Ukrainians have confidence in their national government, the lowest of any electorate in the world, a Gallup poll published in March showed.

Zelenskiy has tapped into this anti-establishment mood, although his inexperience makes Western officials and foreign investors wary.

His campaign has relied heavily on social media and comedy gigs of jokes, sketches and song-and-dance routines that poke fun at his political rivals.

Zelenskiy's campaign blurred the line between reality and the TV series in which he plays a scrupulously honest history teacher who accidentally becomes president.

‘He embodies the perceived need for 'new faces' in politics and could sway the young, pro-reform electorate to his side,’ said Economist Intelligence Unit analyst Agnese Ortolani.