Brazil's presidential election is headed for a run-off vote, electoral authorities said on Sunday, after President Jair Bolsonaro's surprising strength in the first-round spoiled rival Luiz Inacio Lula da Silva's hopes of an outright win.

Brazil's Luiz Inacio Lula da Silva maintains a 13-percentage-point lead over President Jair Bolsonaro, but the far-right incumbent has narrowed his leftist rival's advantage ahead of the October election, according to a poll published on Thursday.