Voting ended at 17:00GMT amid fighting and threats from separatists that prevented residents in English-speaking regions from casting their ballots. Results are expected in two weeks.
Biya, Africa’s oldest leader who has been in office since 1982, claimed the voting was “peaceful” across the country with more than 20 million people.
“I am satisfied after performing my civic duty and particularly satisfied that the election is taking place in calm and serenity and without fighting,” Biya said after voting.
“I hope that the calm will continue after results are proclaimed,” he said.
Cameroon’s fractured opposition was unable to rally behind a strong challenger to the 85-year-old leader.
Main opposition Social Democratic Front party candidate Joshua Osih voted in the country’s economic capital, Douala, and called for transparency in the vote count.
“My wish is that the results of the ballot should not be tampered with. That transparency should be the watchword and that the choice made by the Cameroonian people be respected,” he said.
Even as the candidates spoke, violence had already marked the voting.
The military killed two armed men in the English-speaking northwest town of Bamenda, according to Governor Deben Tchoffo of the Northwest region.
“We shall not allow terrorists to disrupt the election,” he said. “I salute the maturity of people who are braving the threats and carrying out their civic duties. We are informed that armed men are shooting indiscriminately to frighten voters, we shall not allow such a thing to happen.”
Gunfighting between the military and separatists began on Saturday in at least six towns and villages including Nkambe, Mamfe and Kumbo.
Several buildings were burned, including residences where voting material was thought to have been stored.
Several armed men were also killed by the military in the southwest region, Governor Bernard Okalia Bilai confirmed.
“The wave of attacks will not deter us from doing our job,” said Enow Abrams Egbe, chairman of the election commission.
The Election Commission and government said they made provisions for displaced voters, but it was not clear if people came out amid threats by separatists.
Cameroon is also battling Boko Haram fighters in its far north, where more than more than 230,000 people have been displaced.