Exit polls and early counting put 41-year-old Volodymyr Zelenskiy, who plays a fictional president in a popular TV series, comfortably ahead of incumbent President Petro Poroshenko in the first round, though short of a majority.

Zelenskiy's rise coincided with voters around the world upending the status quo, propelling anti-establishment forces such as U.S. President Donald Trump and Italy's 5-Star movement to power.

He must convince voters he is fit to lead a country at war and at the center of the West's tussle with Moscow after the 2014 Maidan street protests ejected Poroshenko's Kremlin-friendly predecessor and Russia annexed Crimea.

Investors are also watching to see if the next president will 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.