Ivory Coast votes in a tense election on Saturday after an opposition boycott and clashes over President Alassane Ouattara's contested attempt to secure a third term.
At least 30 people have been killed in pre-election violence, evoking memories of a 2010-2011 crisis that turned Abidjan into a battleground and left 3,000 dead.
A former IMF official in power since 2010, Ouattara is facing off with veteran opposition leader Henri Konan Bedie in a feud that has marked Ivorian politics for decades.
The vote in French-speaking West Africa's economic powerhouse is also a crunch test in a region where Nigeria faces widespread social protests, Mali is emerging from a coup and jihadist violence is challenging the Sahel.
Polling stations open at 8am (0700 GMT).
Ouattara, 78, was supposed to step aside after his second term to make way for a younger generation, but the sudden death of his chosen successor forced a change in plan.
The Ivorian leader says a constitutional court ruling approved his third term, allowing him to bypass two-term presidential limits after a 2016 legal reform.
His supporters expect a win, touting his record in bringing infrastructure projects, economic growth and stability to the world's top cocoa producer after a decade of instability.
"Since he came to power, there has only been peace in Ivory Coast," said Ouattara supporter Awa Coulibaly at an Abidjan election rally. "We want him to get a first round knock-out win."
But Bedie and opposition leaders say a third mandate is unconstitutional. They accuse the electoral commission and the constitutional court of favouring the government, making a fair and transparent vote impossible.
- Appeal for calm -
The UN has urged calm, but the opposition called for a campaign of civil disobedience to stop the vote, stoking fears of more violence in opposition strongholds.
More than 35,000 police and security force officials have been mobilised to secure the election.
"The question is what will the opposition do after November 1?" said Sylvain N'Guessan, director and political analyst at Abidjan Strategies institute.
Weeks before the election saw sporadic clashes in the south of the country, mainly between local ethnic groups close to the opposition and Diaolu communities from the north who are seen as loyal to the president.
The country's political feuds are often closely tied up with its leader's ethnic identities and regional loyalties.
Police fired tear gas on Friday in the political capital Yamoussoukro to break up fighting between Diaolu youth and opposition-aligned Baoule communities, said local residents.
During its crisis a decade ago, Ivory Coast was emerging from a civil war and the country was split in two, the north held by rebels and the south by forces of then president Laurent Gbagbo.
Ouattara won a long-postponed election in 2010 though Gbagbo refused to accept defeat. After battles in Abidjan, French forces intervened to help Ouattara loyalists oust the former president.
When the outcome of Saturday's elections will be unveiled is unclear. Under the constitution, the electoral commission has five days in which to announce the results.