Anti-French sentiment has risen in Niger since the coup but soured further last week when France ignored the junta's order for its ambassador, Sylvain Itte, to leave.
Reuters reporters said it was the biggest gathering yet since the coup, suggesting that support for the junta - and derision of France - was not waning.
France had cordial relations with ousted President Mohamed Bazoum and has about 1,500 troops stationed in Niger.
On Friday, French President Emmanuel Macron said he spoke to Bazoum every day and that "the decisions we will take, whatever they may be, will be based upon exchanges with Bazoum."
West Africa's regional bloc ECOWAS has slapped sanctions on Niger and threatened military action as a last resort.
Persons:
Mahamadou, Paris, Sylvain Itte, Yacouba, Mohamed Bazoum, Emmanuel Macron, Niger's, Bola Tinubu, Edward McAllister, David Holmes
Organizations:
REUTERS, Police, France, ECOWAS, Thomson
Locations:
Niamey, Niger, NIAMEY, Niger's, West, Central Africa, France, West Africa, Mali, Burkina Faso, Africa's, United States