The 64-year-old, who was elected as Niger's president two years ago, is a key Western ally in the fight against Islamist militants in West Africa.
Youths in supporters of the coup in Niger have taken to the streets to protest.
They were seen attacking the headquarters of the ousted president's party and politicians before setting the headquarters on fire.
The youths also were seen stoning and burning cars outside.
In shocking scenes, groups of civilians with some holding Russian flags in beating up politicians who were allies of President Mohamed Bazoum - who was taken captive on Wednesday.
Following the TV announcement on Thursday by some soldiers of a successful coup, Russia joined other countries and the UN in calling for Bazoum's release.
The 64-year-old, who was elected as Niger's president two years ago, is a key Western ally in the fight against Islamist militants in West Africa.
The US and France, who colonized Niger, both have military bases in the uranium-rich country - and have condemned the coup.
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