Police in the Ukrainian city of Vinnytsia have arrested three people after nationalist demonstrators attempted to derail a campaign appearance by President Petro Poroshenko.

Poroshenko has faced regular protests by ultra-right activists accusing him of corruption as he campaigned for a second five-year term in Sunday's election.

Police said several hundred members of ultranationalist groups showed up at Poroshenko's campaign rally in Vinnytsia in central Ukraine Wednesday, demanding the jailing of Poroshenko's associates who are accused of involvement in a military embezzlement scheme.

The local police said three activists who hurled stones and sprayed tear gas at officers were arrested.

Polls have shown popular comedian Volodymyr Zelenskiy leading the race, followed by Poroshenko and former Prime Minister Yulia Tymoshenko.