Opposition supporters took part in a demonstration in the streets of Niamey on Tuesday after Bazoum was announced the winner of elections.
The protest also comes after Ousmane Mahamane accused the outgoing President Mahamadou Issoufou and his camp of being persistent in defying the sovereign people of Niger.
Ousmane also said the results being published are in many cases not in conformity with the expression of the will of the people.
The Independent National Electoral Commission (CENI) had not yet published the final provisional results, but the vast majority of the results collated from communes were published on its website, giving leader of the Niger Party for Democracy and Socialism Mohamed Bazoum the win.
Bazoum got 39.3% of the vote in the first round of December 27, 2020 elections while Ousmane managed almost 17%.