Benin's presidential election is to go to a second round, as no candidate has the 50% needed to win.
Mathieu Kerekou has ruled Benin for 19 years
Former West African Development Bank head and political novice Yayi Boni won the first round with 35.6%.
In the run-off, he will face former speaker of parliament Adrien Houngbedji, who got 24.2%.
President Mathieu Kerekou was barred from standing, as was long-time rival Nicephore Soglo, as they are both over the constitutional age limit of 70.
The election was seen as a key moment in Benin's history.
Several complaints have been sent to the Constitutional Court to adjudicate on.
The run-off was due next Sunday but the AFP news agency says the Constitutional Court must first rule on the complaints.
International observers praised voters' discipline but have yet to comment on the fairness of the vote counting, AFP reports.
The next strongest candidate, Bruno Amousso, had less than 20% of the vote. There were 23 other candidates.
On the eve of the election, Mr Boni's camp accused the election body of irregularities, such as "missing voting materials, late opening of polling stations and inflated voter lists".
President Kerekou also warned of attempts to rig the vote.
Mr Kerekou came to power as a Marxist but eventually opened up his country to multi-party democracy.
Mr Soglo was president for five years in the 1990s.
Benin is one of the 20 least developed countries in the world.