Flávio Bolsonaro, a Brazilian senator, presidential hopeful and son of embattled former leader Jair, says he is "very happy" to have led in the first round and to be heading into the runoff, with incumbent Lula expressing disappointment over "unexpected" results.
Brazilians are voting across the country, with polls open from 8:00 to 17:00 Brasília time. As voting is digital, first results should appear within three hours of closing.
Brazilian President Luiz Inácio Lula da Silva and Flávio Bolsonaro have a final chance on Saturday to sway voters at rallies in crucial São Paulo before a tight election marked by scandals and personal attacks.