Ivory Coast was set to elect a president on Saturday in a poll feared to cause unrest and threaten political stability.
More than 20 people have been killed in violence in the run-up to the vote, Human Rights Watch said on Friday.
The government banned public demonstrations in mid-August, and security forces have repeatedly disbanded opposition protests and arrested demonstrators in violent clashes.
Four candidates are competing for the highest office. Incumbent President Alassane Ouattara, who has been in power since 2011, counts as the strongest candidate by far.
The 78-year-old previously promised he would step down after his second term, but announced his candidacy in August, a month after the sudden death of his anointed successor, former prime minister Amadou Gon Coulibaly.
Ivory Coast’s constitution allows for only two five-year presidential terms, but Ouattara’s Rally of the Republicans party argues a 2016 constitutional amendment has reset the clock.
The incumbent’s key rivals, Konan Bedie, 86, Pascal Affi N’Guessan, 67, both say Ouattara’s third-term bid is unconstitutional and have called for an election boycott and civil disobedience.
Bedie, a former president from 1993–99 and leader of main opposition party Democratic Party of Cote d’Ivoire – African Democratic Rally, counts as the biggest threat to Ouattara’s re-election.
N’Guessan, a former prime minister who leads the Ivorian Popular Front (FPI) party, also counts as a strong opponent.
The fourth candidate, Konan Kouadio Bertin, 51, is an independent who analysts predict has slim chances.
Roughly 7.5 million Ivorians are due to cast their vote at more than 22,000 polling stations between 7 am and 5 pm (0700-1700 GMT).
A candidate needs to garner at least 50 per cent of votes to win in the first round.
Results are expected to be announced within three days after the vote.