Former Brazilian President Luiz Inacio Lula da Silva holds a solid polling lead going into Sunday's election against incumbent Jair Bolsonaro, with a chance of clinching the race in the first round, fresh surveys showed on Saturday.

Brazil's most polarised election in decades will decide whether to return to power the leftist leader who spent time in jail on corruption convictions or the right-wing populist who has attacked the voting system and threatened to contest defeat.

Two polls released on Saturday showed Lula (above) with a majority of valid votes, which would mean outright victory, avoiding a bruising runoff.

Pollster IPEC showed Lula winning 51 percent of valid votes, excluding blank and spoiled ballots, and a Datafolha poll showed the popular two-term president with 50 percent of valid votes.

Both surveys, from some of Brazil's most established polling teams, had a margin of error of two percentage points and showed Lula with an advantage of 14 percentage points over Bolsonaro.

Two other polls released on Saturday by CNT/MDA and Genial/Quaest showed Lula with 48 percent and 49 percent of valid votes respectively, within the margin of error of outright victory.

If none of the 11 presidential candidates gets more than 50 percent of valid votes, the two front-runners – almost certainly Lula and Bolsonaro – would go to a second-round vote on Oct 30.

Lula told reporters he was hoping to finish the election on Sunday: "I can only be optimistic. There is very little to go to reach 50 percent plus one vote," he said.

Bolsonaro, a 67-year-old former army captain who spent nearly three decades in Congress pushing his pro-gun, anti-gay and anti-abortion agenda, was swept into office in 2018 on a wave of conservative backlash to Lula's Workers Party.

He closed his re-election campaign with motorcycle rallies in Sao Paulo and the southern state of Santa Catarina.

Lula rode in an open car and then walked with thousands of cheering supporters who turned out in central Sao Paulo, eager to see him despite drizzling rain. The event was called the "Walk of Victory."

The Workers Party has booked a rally on Sao Paulo's midtown Paulista Avenue for Sunday night to celebrate victory by the 76-year-former union leader, who co-founded the party in 1980 and has run six times on its presidential ticket.

Brazil's electronic voting system, which Bolsonaro has called vulnerable to fraud without providing evidence, allows the national electoral authority (TSE), to quickly tally results within hours after polls close at 5pm.

The head of the TSE, Supreme Court Justice Alexandre de Moraes, called on Brazilians via Twitter to celebrate the country's democracy by turning out to vote with "peace, security and harmony, respect and freedom."

- Reuters