Niger military officers declared General Abdourahamane Tiani as the new head of state on Friday, saying they had suspended the constitution and dissolved all former institutions after overthrowing President Mohamed Bazoum.
Tiani was the head of the presidential guard that shut Bazoum in his palace on Wednesday and then declared it had ousted him because of bad governance and worsening security.
The general appeared on state television on Friday, with a banner on the screen that described him as the president of a newly formed military council, the National Council for Safeguarding the Homeland (CNSP).
"The President of the CNSP is the head of state. He represents the state of Niger in international relations," an officer said, reading out a statement.
The constitution has been suspended and the government dissolved, and the CNSP will exercise all legislative and executive power, the statement said.
Alarms raised for African nations
African countries and Western powers have reacted with alarm to the events in Niger, insisting that constitutional order be restored.
Niger borders three countries - Mali, Burkina Faso and Chad - that have also experienced military coups in the last two years. Before the uprising this week, it was seen as the West's most stable and solid partner in a region facing a growing Islamist insurgency.