The official count in Mexico's presidential election concluded Friday with results showing that presidential candidate Enrique Pena Nieto got about 3.3 million more votes than his closest rival, giving him a 6.6 per cent lead in the former ruling party's bid to regain power.

The count by the country's electoral authority, which included a ballot-by-ballot recount at more than half of polling places, showed Pena Nieto getting 38.21 per cent of votes. His top challenger, leftist Andres Manuel Lopez Obrador, got 31.59 per cent. The final count was almost exactly the same as the quick count released hours after the elections.

The results, out of roughly 50.3 million valid ballots, will almost certainly become the target of legal challenges by Lopez Obrador. He alleges that Pena Nieto's Institutional Revolutionary Party, or PRI, engaged in vote-buying that illegally tilted millions of votes. PRI officials deny the charge.

Josefina Vazquez Mota of the conservative National Action Party got 25.41 per cent of votes cast in Sunday's elections, and the small New Alliance Party got 2.29 per cent, barely passing the two-per cent barrier needed to preserve the party's place on future ballots.

Almost 2.5 per cent of ballots where voided; while some voters in Mexico void their ballots as a form of protest, some also simply make mistakes in marking them.

The final vote count must be certified in September by the Federal Electoral Tribunal. The tribunal has declined to overturn previously contested elections, including a 2006 presidential vote that was far closer than Sunday's.

Accusations of vote-buying

Accusations of vote-buying began surfacing in June, but sharpened early this week as thousands of people rushed to grocery stores on the outskirts of Mexico City to redeem pre-paid gift cards worth about 100 pesos ($7.50). Many said they got the cards from PRI supporters before Sunday's elections.

Lopez Obrador said millions of voters had received either pre-paid cards, cash, groceries, construction materials or appliances. Lopez Obrador would not rule out street protests, like the one he led in 2006 to protest alleged fraud in the presidential elections of that year, which he narrowly lost to President Felipe Calderon.

But he said Thursday that his challenge of the results would be channeled through legal venues, like the electoral institute and courts.

"We have acted and we will continue to act in a responsible way, adhering to the legal procedure. Nobody can say we are violating the law," Lopez Obrador said.

Leonardo Valdes, the president of the Federal Electoral Institute, said he doesn't see any grounds for overturning the results.

"I do not see any justification for rejecting the entirety of the election results," Valdes said. "Rejecting the results would be like rejecting the effort of those 50 million voters."