- The opposition has long accused the authorities of working to re-elect Biya, pointing to his party's slick rallies and massive distribution of Biya-branded merchandise.
- But despite the ubiquity of Biya's posters across Cameroon, he has been virtually invisible during the campaign, except for a single event last weekend.
- In a bid to limit disruption to the polls, authorities have imposed stringent security measures including the suspension of all inter-regional road, rail and air travel.
Cameroonians are voting in crunch presidential polls on Sunday, with octogenarian leader Paul Biya seeking a seventh term against a backdrop of unprecedented violence in the country's English-speaking regions.
The vote follows a last-minute opposition unity bid to dislodge the 85-year-old incumbent, one of Africa's longest-serving rulers.
Two leading opponents have formed the first electoral union since 1992, but talks between the array of other opposition parties to create a "super-coalition" to deny Biya another seven years were apparently unsuccessful.
In the Bastos public school in the capital Yaounde, where Biya will later cast his vote, brisk voting got underway as soon as the polls opened.
"I feel proud," said Patrick, 38, an airport worker after voting. "I want the next president to consolidate what we have achieved in Cameroon. I want the elections to pass off peacefully, that's my only hope for the polls."
Voters in the queue were watched by a heavy security presence including members of the presidential guard, deployed ahead of Biya's arrival.
Cameroon's 6.5 million eligible voters are casting their ballots as the toll continues to mount in the anglophone southwest and northwest, which have been rocked by a separatist insurgency launched a year ago against the mainly francophone state.
The violence has claimed the lives of at least 420 civilians, 175 members of the security forces and an unknown number of separatists, according to the International Crisis Group (ICG) think-tank.
In Buea, capital of the southwest, three separatists of the so-called Ambazonia Republic were gunned down on Friday while a priest was executed by soldiers on Thursday, according to witnesses.
The far north is also mired in insecurity, as Nigeria-based Boko Haram fighters mount attacks despite efforts by the US to equip and train Cameroon's military to battle the jihadists.
In a rare coordinated political manoeuvre, one of the key opposition front runners, Maurice Kamto, agreed late Friday to a unity deal between his Movement for the Rebirth of Cameroon (MRC) and the People's Development Front (FDP), meaning he will stand on behalf of both parties.
It is the first such tactical pre-election tie-up since John Fru Ndi stood as the sole opposition candidate in 1992 in polls that his supporters say he won, but allege were manipulated to hand victory to Biya.