KIEV, Ukraine (AP) — Police have moved in to stop a scuffle between supporters of rival candidates in Ukraine's presidential election.

Comedian Volodymyr Zelenskiy, who stars in a widely popular TV sitcom about a schoolteacher turned president, easily beat President Petro Poroshenko in the first round on March 31. Zelenskiy garnered 30% of the vote, while Poroshenko won just under 16%, and a runoff between them is set for April 21.

Supporters of Zelenskiy and Poroshenko clashed Tuesday in front of Zelenskiy's campaign headquarters in Kiev, as they tried to wrest campaign posters from each other. Police quickly intervened, detaining two people.

Zelenskiy's office said he wasn't in the building when the brawl occurred.

Ahead of the vote, Zelenskiy and Poroshenko are to hold a debate in in Kiev's Olimpiskiy Stadium, Ukraine's biggest arena.