Comedian Volodymyr Zelensky is set for a landslide win in Ukraine's presidential election. (Photo: AFP/Genya Savilov)

Zelensky, whose only previous political role was playing the president in a TV show, trounced incumbent Petro Poroshenko in Sunday's election in a stinging rebuke to the establishment fuelled by anger over war and social injustice.

Ukrainians looked to the future with hope and anxiety after the performer took 73 per cent of the vote, according to nearly complete official results.

The star of the sitcom "Servant of the People", now in its third season, has vowed to stick to the pro-European course set out by his predecessor.

But he has also said he will try to improve ties with arch-enemy Russia.

On the streets of Kiev, many praised honest elections and a peaceful transfer of power after popular uprisings of 2004 and 2014.

"People showed that they want change," 28-year-old Karina told AFP.

"We had the most honest polls in the history of Ukraine," she added, praising Poroshenko for conceding defeat soon after exit polls were published.

Zelensky - who at 41 will be Ukraine's youngest ever president - presented a vague manifesto and one of his campaign slogans was, "No promises. No apologies".

Zelensky's campaign started as a joke but struck a chord with voters frustrated by social injustice, corruption and a war with Russian-backed separatists in eastern Ukraine. (Photo: AFP/Sergei Supinsky)

He shunned traditional campaign rallies, instead performing comedy gigs, and implied he would use the same unorthodox style to run the country of 45 million dependent on international aid.

It remained unclear on Monday who would fill top positions, including the role of prime minister.

RUSSIA SEES 'CHANCE'

US President Donald Trump and French leader Emmanuel Macron called the political novice to congratulate him on his landslide win.

"Allow us to express our appreciation for the strong attachment to democracy and the rule of law that the people of Ukraine have demonstrated," EU Council President Donald Tusk and European Commission head Jean-Claude Juncker said in a joint letter to Zelensky.

Outgoing Poroshenko said he stood ready to help his successor, despite a bitter campaign.

Russia - which Kiev and the West accuse of fuelling a smouldering separatist conflict in Ukraine's industrial east - said it saw an opportunity with the new leader.

Russian Prime Minister Dmitry Medvedev said there was "a chance" to improve ties.

"What's needed for this? Honesty. And a pragmatic and responsible approach," Medvedev wrote on Facebook.

There was no immediate comment from President Vladimir Putin.

Ties between Ukraine and Russia were shredded after a bloody uprising ousted a Kremlin-backed regime in 2014, prompting Russia to annex Crimea and support insurgents in a conflict that has claimed around 13,000 lives.

Zelensky has said that among his top priorities are winning the release of Ukrainians being held by Russia and rebooting Western-brokered peace talks.

"I will never let you down," Zelensky told jubilant supporters at his campaign headquarters where he was showered with colourful confetti on Sunday night.

"I can tell all post-Soviet countries: 'Look at us! Everything is possible!'," he declared.

The remark appeared aimed at Russia, where Putin has been in power for 20 years and many have followed the Ukrainian election with keen interest.

Poroshenko said that he would leave office but would not quit politics.

His faction has the most seats in the legislature and new parliamentary polls are due in October.

The Ukrainian president has strong powers over defence, security and foreign policy but will need parliament backing to push through reforms.

VNF/AFP