UPDATE 7-Right-winger leads Brazil election, heading for run-off

Right-wing Congressman Jair Bolsonaro took a commanding lead in Brazil's presidential election on Sunday.

Right-wing Congressman Jair Bolsonaro took a commanding lead in Brazil's presidential election on Sunday, but the contest was likely to extend to the second round of voting between him and leftist former Sao Paulo Mayor Fernando Haddad, according to exit polls and initial results.

With 79 per cent of votes counted, Bolsonaro had received 48 per cent of valid votes, far ahead of Haddad's 27 per cent but short of the outright majority needed to avoid an Oct. 28 runoff.

An exit poll of 30,000 voters conducted by survey institute Ibope suggested Bolsonaro would win 45 per cent of valid votes on Sunday, with 28 per cent going to Haddad. The survey had a margin of error of plus or minus two percentage points.

Bolsonaro, a former Army captain who praises dictatorships and vows a brutal crackdown on crime and graft, surged in recent opinion polls on a wave of antipathy towards Haddad's Workers Party, whose leader is in jail for after a corruption conviction.

Bolsonaro, 63, gained momentum after a near-fatal stabbing at a rally one month ago that kept him from campaigning. He had appealed via social media for voters to hand him a first-round victory with a 50 per cent result.

Supporters rallying outside his Rio de Janeiro home waved the green-and-yellow national flag, chanting "Our president!" when he returned from voting, accompanied by a nurse, in a convoy of black SUVs.

Haddad's campaign headquarters in a Sao Paulo hotel broke out in cheers when exit polls showed that the race would go to a runoff. Some recent polls have shown he could beat Bolsonaro in the second round.

Still, exit polls showed big state-level wins by allies of Bolsonaro in surprise upsets and major defeats for Workers Party candidates, including impeached former President Dilma Rousseff running for a Senate seat.

Haddad, a former education minister and one-term mayor of Sao Paulo, is standing in for the party founder, former President Luiz Inacio Lula da Silva, who is serving time for bribery and money laundering.

Bolsonaro is riding a wave of anger at the establishment over one of the world's largest political graft schemes and rising crime in the country with the most murders in the world. His supporters blame the Workers Party, which ruled Brazil for 13 of the past 15 years, along with reckless economic policies that contributed to Brazil's worst recession in a generation.

In the most polarized election since the end of military rule in 1985, Bolsonaro is backed by a group of retired generals who have criticized the 2003-2016 Workers Party governments and publicly advocate military intervention if corruption continues.