Four soldiers and a journalist were also injured in yesterday's attack, other sources said.
"The minister's convoy was attacked in the Kumba area," the security source said.
The ambush occurred in the heartland of an armed campaign to gain independence for the Northwest and Southwest Regions, a predominantly English-speaking part of the French-speaking West African state.
Years of resentment at perceived discrimination at the hands of the francophone majority fuelled demands in 2016 for a return to the country's federal structure.
Biya took a hard line, ruling out any concessions.
As the situation polarised, anglophone militants last October 1 made a symbolic declaration of independence.
They named Buea, the main town of Southwest Region which lies close to Kumba, as the capital of their purported state, Ambazonia, which has no international recognition.
A government crackdown then followed, plunging the two regions into almost daily acts of violence and retribution that have claimed scores of lives and forced tens of thousands from their homes.
The crisis has cast a dark shadow over a presidential election scheduled for October 7 -- a fact that Biya, who has been head of state for 35 years, appeared to acknowledge in his announcement on Twitter.
"I will be your candidate in the next presidential election," he said, adding that he was "aware of the challenges that we must face together for a Cameroon that is even more united, stable and prosperous".
According to a government report last month, separatists have killed 74 soldiers and seven police since late 2017 while more than 100 civilians had died "over the past 12 months."
The presence of a large English-speaking minority in Cameroon dates back to the colonial period.
The French colony gained independence in 1960, becoming Cameroon. The following year, the British-ruled Southern Cameroons were amalgamated into it, giving rise to the Northwest and Southwest regions.
The fighting has had a dramatic impact on civilian life.
UN says 160,000 people have been internally displaced and 20,000 have sought refuge in neighbouring Nigeria.
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)