RIO DE JANEIRO, Oct. 7 (Xinhua) -- Brazil's presidential front-runners, right-wing Jair Bolsonaro and his left-leaning rival Fernando Haddad, are expected to face off in a run-off later this month, according to preliminary results.

With 96 percent of the votes counted, Bolsonaro garnered 46.66 percent while Haddad secured 28.43 percent, according to results from the top electoral body Superior Electoral Court (TSE).

Center-left candidate Ciro Gomes came in third with 12.52 percent of the votes, compared with 4.83 percent for Geraldo Alckmin of the Brazilian Social Democracy Party (PSDB).

Voter turnout was 79.67 percent, or more than 112 million out of some 147 million eligible voters cast their ballots, leaving the abstention rate at 20.33 percent. Voting is mandatory in Brazil.

Some 91.22 percent of the votes cast were valid, while 2.67 percent of the ballots were left blank and 6.11 percent were nullified.