Mali's presidential election will go to a second round on August 11 after no candidate managed to secure a majority in the crunch poll, which the runner-up says is tainted by fraud.
Figures for Sunday's ballot announced on live television showed former prime minister Ibrahim Boubacar Keita in the lead with 39.2 per cent of the vote, ahead of main rival Soumaila Cisse with 19.4 per cent.
But Cisse accused the government of allowing widespread fraud after the interior ministry said more than 400,000 ballot papers had been spoiled out of some 3.5 million votes cast.
"The high turnout on July 28 should not distract from the unpreparedness, poor organisation and fraud that have characterised the first round of the presidential election," Cisse told a media conference in Bamako.
The 63-year-old said he was "astonished" by the high number of spoiled ballots and would be asking Mali's constitutional court to investigate.
"In preparation for the second round, I urge the government of Mali and its partners to take strict measures to ensure a clean and clear expression of the will of the people," he added.
Cisse, formerly finance minister and chairman of the Commission of the West African Economic and Monetary Union, said "thousands, or even tens of thousands" of Malians were unable to find their names on voting lists, or even the correct polling station.
His comments came after his party said the election had been marred by people submitting multiple votes.
A credible election is seen as key to Mali's recovery after a coup in March last year overthrew Amadou Toumani Toure, plunging one of the region's most stable democracies into political crisis and leading to an Islamist insurgency.
The official turnout was recorded at 51.5 per cent, eclipsing Mali's previous best of 38 per cent.
Despite heavy security during voting amid fears al-Qaeda linked militants would attack polling stations, no serious incidents were reported on election day.
