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.

Paul Biya, the world's oldest head of state, claims victory in a disputed election, sparking unrest across the country already grappling with violence, corruption, and political tension.

At least four protesters were killed during clashes with security forces in Cameroon as opposition supporters rallied to demand credible results from the recent presidential election, the local governor said late Sunday.

Cameroon's opposition leaders rejected presidential election results that extended President Paul Biya's rule for another seven years, saying the outcome did not reflect the will of the people in a country already battling a separatist conflict.