Mexico City - A recount on Thursday showed Mexico's Enrique Pena Nieto as the clear winner of Sunday's presidential election, but the runner-up still refused to concede, alleging Pena Nieto's party bought millions of votes.
The results set up a return to power for the Institutional Revolutionary Party, or PRI, which governed Mexico from 1929 to 2000, when it was frequently accused of vote-rigging.
With 99% of polling stations counted or recounted, Pena Nieto held 38.2% of the vote, 6.7 points ahead of leftist Andres Manuel Lopez Obrador.
Mexico's Federal Electoral Institute, or IFE, expected to conclude the final recount later on Thursday and certify the results on Sunday, when an official count of the congressional elections was also due.
Pena Nieto claimed victory last Sunday when initial results showed him winning about 38% of the vote, about 6.5 points more than Lopez Obrador. Trailing in third was Josefina Vazquez Mota of the ruling conservative National Action Party, or PAN.
Lopez Obrador asked for a full recount, but the IFE said it would only recount ballots from 54% of polling stations, saying it was guided by specific conditions of election law.
"It's clear that I have won these elections with a wide margin of the vote," Pena Nieto told CNN on Thursday, saying there were "no grounds" for allegations of vote-buying.
The PRI called for an investigation by the attorney general's office into what it considered false accusations.
Pena Nieto has already been congratulated by outgoing President Felipe Calderon and leaders such as US President Barack Obama and Brazilian President Dilma Rousseff.
Lopez Obrador alleged widespread irregularities and gave a news conference on Thursday in front of a wall of gift cards he said the PRI distributed to voters before the balloting, allowing them to buy merchandise at retail chain Soriana, which has denied its cards were used to buy votes.
The 58-year-old Lopez Obrador said some of the voters had turned in their cards to his leftist coalition in regret at selling their votes.
"The magnitude of the vote-buying is becoming apparent: Billions of pesos and millions of votes bought," said Lopez Obrador, who trailed Pena Nieto by more than 3.3 million votes.
The fiery orator could still challenge the recount with the country's electoral tribunal, even though electoral officials all but ruled out any changes in the outcome.
"There is no reason not to fully recognise the voting results," said Leonardo Valdes, president of the IFE board.
Vazquez Mota of the PAN levied similar accusations that vote-buying took place ahead of the vote, but accepted defeat.
"We need the electoral authority to review in detail the campaign spending that evidently surpassed the limits established by the law and moreover was associated with buying and coercing voters," she told reporters.
"We should correct these inequalities so that we can have conditions of genuine competition and full democracy."
Lopez Obrador also challenged the outcome when he finished a much closer second in the 2006 presidential election. He refused to concede then and called for street protests that blocked the main boulevard in Mexico City for weeks.