Senegal's leader Abdoulaye Wade has admitted that he will now go to a run-off after failing to win more than 50% in the first round of voting.
"The numbers are clear, we are headed to a second round," his spokesman Amadou Sall said.
Unofficial figures show Mr Wade, 85, is likely to face former Prime Minister Macky Sall in the run-off.
European Union observers have criticised the lack of official results from Sunday's contentious elections.
Senegal's election commission has yet to release any provisional results, which are being announced by local media as they trickle in from polling stations.
Earlier unofficial results - with more than half of the vote counted - gave Mr Wade 32%, with his closest rival Macky Sall on 25%. There were 12 other candidates.
Analysts say Mr Wade is likely to struggle in the second round, when the field narrows to two candidates.
Mr Wade's bid for a third term has sparked weeks of violent protests, leading to about six deaths.
Polling day itself was largely peaceful - but the BBC's Umaru Fofana in Dakar says people are now becoming impatient and suspicious that there are no official results.
Election officials previously said provisional results would be available on Tuesday - but then put that back to Friday, saying they were acting within the law.
EU observers have questioned this delay.
"In the internet-era, it is inconceivable that the Senegalese will need to wait until Friday to know the official results,'' the head of the delegation of European parliamentarians, Cristian Dan Preda said.
A second round - due on 18 March - is inevitable, according to foreign observers.
"Any other outcome seems statistically impossible after what we know and hear," EU observer mission chief Thijs Berman said.
Until late on Monday, Mr Wade had been confident that he would be able to get enough votes to win an outright victory.
"To all of my supporters, my allies, my sympathisers, I ask that you remain mobilised," Mr Wade read from a prepared statement as he met reporters for the first time since the elections.
"At this very hour... everything is still possible - victory or a run-off," he said.
Our correspondent says the president also said that he would be opening talks with opposition candidates ahead of the second round.
The president was booed as he cast his vote on Sunday in the capital, Dakar - and he lost in his own constituency in the middle-class Dakar neighbourhood of Point E, Senegal's national APS news agency reports.
Mr Sall, who is running for the first time, told the BBC that it would be "easy" to win in the second round, as he said all opposition candidates had agreed to unite behind whoever emerged as Mr Wade's challenger.
Senegal's constitutional court ruled in January that Mr Wade could stand again on the grounds that his first term had not counted since it began before the two-term limit was introduced in 2001.
Senegal, a former French colony, is seen as a stable democracy with an unbroken series of elections since independence in 1960.
It remains the only West African country where the army has never seized power.