"The belief is that the head of a bald man contains gold," said Afonso Dias, a police commander in Mozambique's central Zambezia province.
Albino people have also been killed in the region for ritual purposes.
Three men have been killed in the past week alone.
The BBC's Jose Tembe in the capital, Maputo, says police think the notion of a bald head containing gold is a ruse by witchdoctors to get clients to take a person's head to them.
"Their motive comes from superstition and culture - the local community thinks bald individuals are rich," a police commander told a press conference in Maputo.