Lawyer and anti-corruption campaigner Zuzana Caputova has easily won the first round of Slovakia's presidential election, BBC reported.
She has just over 40% with Maros Sefcovic of the ruling Smer-SD party her nearest rival on less than 19%.
Ms Caputova came to prominence during mass protests sparked by the murder of a journalist who had been investigating political corruption.
As no candidate won more than 50%, a second-round run-off will be held.
Turnout was just under 50%.
If Ms Caputova, 45, wins the second round in a fortnight's time, she will become Slovakia's first female president.
"I see the message from voters as a strong call for change," she said early on Sunday.
A member of the small Progressive Slovakia party, which has no seats in parliament, she is a newcomer to politics, whereas her conservative 52-year-old opponent is vice-president of the European Commission.
Ms Caputova first rose to prominence when she led a battle lasting 14 years against an illegal landfill.