The villages of Oku and Mbessa have fought for decades over land rights in the area.
"All five people killed were from Oku. Security reports from the area say the confrontation was quite fierce and bloody," the aide was reported as saying.
Battles over land and natural resources, especially at the start of the farming season, are a regular feature of life in rural Cameroon, where many people are subsistence farmers.
Villagers in the North-West province burned down some 300 homes and forced thousands of people to flee a rival settlement in March.
Two years ago, villagers in the province beat their chief to death and burned his corpse after they accused him of selling farmland to wealthy cattle breeders.
They then stoned to death the policeman who came to arrest the main suspect.