The presidential election in Ivory Coast may enter a second round after partial results point to a tight race between the chief candidates.

Partial results from an election aimed at reuniting war—divided Ivory Coast showed President Laurent Gbagbo with a slight lead Wednesday over the main opposition leader.

Electoral commission spokesman Bamba Yacouba announced results from about half the country’s 5.7 million registered voters in a late night state television broadcast that stretched into the early hours of Wednesday.

The figures indicated Mr. Gbagbo was ahead with nearly 37 percent the vote, while his main rival, opposition leader Alassane Ouattara, had 34 percent of the vote, according to an Associated Press tabulation. Ex—president Henri Konan Bedie was in third place with about 27 percent.

If no candidate wins a simple majority, the top two finishers in this West African nation’s vote will face off in a second round on November 28. The electoral commission is expected to continue releasing results later Wednesday, culminating in a final tally by day’s end.

The vote, the first since a brief civil war split the world’s No. 1 cocoa producer in two, is seen as a critical turning point in Ivory Coast’s history. Many hope it will restore stability and reunify the country, but some worry it could trigger unrest if political rivals fail to accept the outcome.

Uncertainty and a lapse in releasing results from Sunday’s poll have fuelled new fears of possible unrest. On Tuesday, many businesses and restaurants in the main city, Abidjan, shut down or sent workers home early, and highways in the skyscraper—lined city were void of usual traffic jams.

The head of the armed forces, Gen. Phillipe Mangou, went on state television to urge residents to go back to work as normal and stay calm.

Earlier Tuesday, the head of the European Union’s 120—strong observer mission, Cristian Preda, criticized the electoral commission for delaying the release of results, saying the delay was fuelling tension among a nervous electorate.

Election officials blame logistic problems and heavy rains for the delays.

Mr. Preda said the EU had detected no fraud in Sunday’s poll and praised authorities and voters for having carried it out peacefully. But he raised questions about transparency in ballot counting, accusing the electoral commission of barring 14 EU monitors from centres where ballots were being collated in several parts of the country. Those include, crucially, the commission’s headquarters in Abidjan, where national results are being released.

EU observers at the electoral headquarters confirmed separately that since counting began on Sunday night, they had been unable to enter the room where national results are being tabulated.

Yves Tadet, an electoral commission official, said that although monitors could observe counting at polling stations and regional centres across the country, they were not allowed to observe the final tabulation of results at the independent electoral commission headquarters.

The U.S.—based Carter Centre also said one of its monitors had been told to leave a vote counting centre in the capital, Yamoussoukro. But others had no problems and the mission generally praised the electoral process, as did the African Union. The Carter Centre said voter turnout had been higher than expected, at about 74 percent.

The vote had been delayed for five years because of disputes over voter rolls. Mr. Gbagbo, whose five—year mandate officially expired in 2005, stayed in office claiming elections were impossible because of a 2002—2003 war that left rebels in control of the north.

Ivory Coast has been struggling to hold the vote since a 2007 peace deal broke years of political stalemate, leading to the dismantlement of a U.N.—patrolled buffer zone that had marked the divide between the rebel—held north and the loyalist south.

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