Updated

The party of Malian presidential candidate Soumaila Cisse said Wednesday the election had been marred by "ballot stuffing" and demanded the resignation of the minister responsible for the polls.

The accusation came after it emerged that, with about a third of the ballots in Sunday's first round counted, former prime minister Ibrahim Boubacar Keita had taken a wide lead over Cisse and the other candidates.

"We denounce the ballot stuffing. In spite of this, according to our figures, a second round is inevitable to decide between our candidate Soumaila Cisse and Ibrahim Boubacar Keita," Madou Diallo, president of the youth wing of Cisse's Union for the Republic and Democracy (URD), told a meeting of around 1,000 activists.

He did not say which candidate had benefited from the alleged ballot-stuffing, a form of electoral fraud in which people submit multiple ballots during a vote in which only one ballot per person is allowed.

Although there were 27 presidential hopefuls, analysts have characterised the election as a two-horse race.

Former prime minister Keita is seen as the frontrunner ahead of Cisse, a former finance minister and erstwhile chairman of the Commission of the West African Economic and Monetary Union.

"It is 100 percent sure there will be a second round. The minister for territorial administration announced a turnout of 53 percent, according to preliminary results," Diallo added.

"That gives about 3.6 million voters who voted. It means it will take at least 1.8 million votes to win the first round, whereas so far no candidate has more than a million votes."

Abdoulaye Coulibaly, another URD youth leader, said the party's own figures showed Cisse had secured a majority in six of the eight regions of Mali and he vowed that the URD would take legal action to counteract fraud.

"We will lodge an appeal to the constitutional court and you will see that many votes will be cancelled from our opponents," he said.

Other delegates at the meeting accused territorial administration minister Moussa Sinko Coulibaly's department of having "failed in its duties" and called for him to be sacked.

Sunday's vote was the first since an uprising by Tuareg separatists sparked a military coup in March last year which toppled democratically elected president Amadou Toumani Toure, plunging Mali into a political crisis and opening the way for Islamists to occupy the vast desert north for 10 months, before being ousted by a French-led military offensive.

An official announcement of the result is expected on Thursday and if no one gets an outright majority the election will go to a second round run-off on August 11 between the two most popular candidates.