Protester Patrick Siani confirmed the demonstration and arrests.
Saturday is the 50th anniversary of British Cameroon's merger with the former French Cameroon.
The protest follows other unrest this week, ahead of Oct. 9 elections.
On Thursday, gunmen carrying signs opposing President Paul Biya blockaded a bridge and shot at police in the city of Douala.
Biya has ruled since 1982 and is widely expected to win another seven-year term in the West African nation.