Sunday’s protest against what the opposition describes as bad governance had initially been authorized by the government, local journalist Birahim Ousmane said by telephone.
But the authorities cancelled the permission for fear of violence after protests against the French weekly Charlie Hebdo left 10 people dead in the West African country Friday and Saturday.
The demonstrators were protesting the publication of caricatures of the prophet Mohammed by Charlie Hebdo.
The opposition Alliance for Reconciliation, Democracy and the Republic (ARDR) defied orders to cancel its rally in the capital Niamey. Demonstrators hurled stones at police who responded with tear gas.
Those arrested included several leaders of the party. No injuries were reported.