Early signs from the counting of votes in Senegal's presidential election are that incumbent Abdoulaye Wade faces a strong challenge from former premier Macky Sall.

An AllAfrica correspondent reports that after a turbulent election campaign - in which Wade is, controversially, standing for a third term - voters responded with maturity on Sunday, going to the polls with confidence and in large numbers.

As results began to be announced after polling stations closed, Sall cited unconfirmed counts showing he had won in the country's largest regions, including Dakar, Rufisque, Tambacounda, Matam, Louga, Foundiougne, Matam and Boukounling, as well as in the diaspora.

Agence de Presse Sénégalaise reported Sall as saying overnight Sunday that a second round would be needed. "The figures in our possession indicate that a second round is inevitable," he said. He called for "strict compliance" with the popular will.

A candidate needs a majority of all votes cast to be elected in the first round.

Wade was booed by voters in his home district as he went to vote on Sunday.

He was reported as telling the French newspaper, Journal du Dimanche, ahead of voting that his majority would be "so overwhelming" that he would be elected in the first round. Later Radio France Internationale quoted a presidential spokesman as saying it was far too early to tell whether a second round would be needed.

Wade was quoted as telling Journal du Dimanche that France and the United States had called on him to retire because "I am not docile ... I am not a Negro service boy".