More than half of the ballots used in Sunday's Mexican presidential elections will be counted again, the Associated Press reports.

Edmundo Jacobo, executive secretary of the country's Federal Electoral Institute, said 78,012 of the 143,000 ballot boxes used during the July 1 vote - 54.5 percent of the votes - will be opened and counted again, following the discovery of "inconsistencies" in vote tallies.

The preliminary count had Enrique Peña Nieto of the Institutional Revolutionary Party (PRI) as the winner with 38 percent of the vote. But his presumed runner-up, Andres Manuel López Obrador of the Democratic Revolution Party (PRD), has refused to concede, calling for a complete recount of the ballots.

Mexican electoral law allows for a recount in three cases: if there are discrepancies in final vote counts; if the first and second-place finishers are separated by one percentage point or less; or if every vote in a ballot box is for the same candidate.

The announcement of the recount came down amid allegations that the PRI had bought votes: thousands of Mexico City residents flocked to stores on Tuesday to use gift cards they said they got in exchange for supporting Peña Nieto.

"They gave us the cards in the name of the PRI and Rep. Hector Pedroza (a PRI congressional candidate), and they said they were counting on our vote," one cardholder, Maria Salazar told the AP.

Electoral law says gifts can not be used to influence a vote, and cannot exceed campaign spending limits. The National Action Party (PAN), which was the incumbent in this election, accused the Peña Nieto campaign of buying about 9,500 prepaid gift cards worth just over $5 million, but that no direct evidence of vote-buying had been discovered.

[image of Enrique Peña Nieto via Agence France-Presse]