Cameroon's President Paul Biya, the world's oldest serving ruler, secured an eighth term in office on Monday, election results showed, triggering clashes between security forces and opposition supporters who say the vote was rigged.

Backers of opposition candidate Issa Tchiroma Bakary, armed with sticks and stones, blocked off roads with debris and burning tyres in the central African country's commercial capital Douala.

Police fired tear gas at crowds who wore masks or tried to cover their faces with clothing. In other parts of the city, streets that normally buzzed with motorbikes were deserted.

Biya – aged 92, with a new mandate that could keep him in power until he is almost 100 – said the people had once again placed their trust in his leadership and expressed sorrow for the violence in a statement posted on social media platform X.

"My first thoughts are with all those who have unnecessarily lost their lives, as well with their families, as a result of the post-election violence," Biya said. The government has rejected opposition accusations of irregularities.

He also reaffirmed his commitment to building a "peaceful, united and prosperous Cameroon."

Official results published on Monday showed Biya winning the October 12 vote by a comfortable margin of 53.7 percent against 35.2 percent for opposition leader Tchiroma.

While proclaiming the final results, Constitutional Council President Clement Atangana said the election was free and fair.

Tchiroma claimed victory last week and said he would not accept any other outcome. Protests erupted in several towns after early, partial results suggested Biya was on track for victory. The government urged people to wait for the results.

Over the weekend, four people died in clashes in Douala, the opposition said. (Reuters/ Xinhua)