Lula did not win the absolute majority needed to avoid a run-off

Lula failed to secure an outright victory over Geraldo Alckmin in the first round of the election on Sunday.

He secured 48% of the vote, falling short of the 50% required to avoid a run-off on 29 October, officials say.

Mr Alckmin gained ground late in the campaign, after President Lula's party was accused of dirty tricks.

The former Sao Paulo governor took 41.4% of the vote.

The final result was confirmed by the country's electoral court on Monday evening.

Bitter campaign

"Obviously, every candidate would like to win an election in the first round," Lula said at a news conference on Monday.

Mr Alckmin says he can win the second round battle

"But the wisdom of the people doesn't always allow that. So now, we're going to see a fairer, truer campaign with two candidates head to head."

The president said he would not be short of votes in the second round. "Victory will just take a little longer, that's all," he said.

Lula added that he welcomed a full police investigation into the dirty tricks scandal that dominated the end of campaigning.

Mr Alckmin said "everything starts from zero" in the second round.

"Confidence in our candidacy is growing," he said.

Mr Alckmin has tried to steer the debate away from corruption towards what he sees as the key issues - improving education, security, healthcare and the economy's growth rate.

Both candidates agree they want to talk sensibly about the issues rather than trade accusations over corruption.

But according to the BBC's Steve Kingstone in Sao Paulo, behind the scenes their advisers are preparing for a bitter campaign.

Dossier

The president had a comfortable lead in the weeks leading up to the election, but opinion polls showed a dip in support for him amid scandals involving his Workers' Party.

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Two weeks ago two men with links to the party were arrested carrying $800,000 in cash, which detectives believe was to have paid for a dossier of corruption allegations against the president's rivals.

The scandal led Lula to sack his campaign manager, but it resurfaced over the weekend with newspapers publishing photographs of the wads of banknotes.

The president denies ever engaging in smear tactics.

On Friday he pulled out of a final TV debate with other candidates, saying they would launch personal attacks on him.

This move looks to have been a huge tactical error, our correspondent says.

Attention will now focus on the electoral court's inquiry into dirty tricks, with the president himself among those under investigation.

Poverty

It is four years since Lula, the first left-winger to hold the country's highest office in 50 years, was elected in a landslide victory.

His policies, which include raising the minimum wage and broadening state help to the poorest families, have reduced the number of Brazilians living in poverty.

But many commentators argue that his programmes fail to address the structural problems that underpin poverty, such as education.

Mr Alckmin has drawn support from the business community and middle class voters angered by a corruption scandal last year involving government lawmakers.