Mali President Amadou Toumani Toure looks set to win a second five-year term, with partial poll results showing him well ahead of his main rival.
Incumbent President Toure is favourite to win
The electoral authorities say they will announce the full results on Tuesday.
International election monitors said the election appeared to have gone smoothly with no reports of unrest.
But opposition candidates alleged fraud, saying voters' lists favoured Mr Toure and accusing his supporters of using state assets for his campaign.
Results from 64 of the country's 703 districts showed Mr Toure was ahead of his main challenger, Ibrahim Boubacar Keita, with 61.3% of the vote.
Mr Keita, who is trailing Mr Toure with 29.8% of the vote, is the president of Mali's National Assembly and a former prime minister who came third in the 2002 presidential poll.
Announcing the partial results on Monday, a spokesman for the Ministry of Territorial Administration said Mr Toure was on course to win.
"From what has been counted so far, the president has a majority," Oumar Sangare said.
In the capital, Bamako, the president had so far won 54.2% of the vote and Mr Keita 38.8%, Mr Sangare said.
Earlier, Mr Toure's spokesman, Hassan Barry, claimed the president had been re-elected.
"The curve is very clearly in favour of our candidate¿ who is largely ahead, according to the first results sent to us by our representatives at the counting centres," Hassan Barry said.
"In view of these results, he will be elected in the first round with an overwhelming score."
If no candidate wins 50% of the vote in the first round, the two top candidates will compete in a run-off on 13 May.
Mr Toure, known as "ATT", played a leading role in ending Mali's military dictatorship with a coup 16 years ago.
He then organised elections in 1992 and handed power over to the winner, Alpha Oumar Konare.
Mr Toure was elected president in 2002, after Mr Konare had served two terms.