The African Union has given a 15-day deadline to Niger's new junta to return to their bases and restore constitutional order, while the EU and France have suspended security cooperation and financial aid to the country.
General Abdourahamane Tiani declared himself the country's new leader on Friday, citing the security situation, corruption, and economic woes.
The African Union condemned the coup and expressed concern about the resurgence of military overthrows in Africa.
France suspended development aid and budgetary support to Niger, while the EU announced the indefinite suspension of security cooperation and budgetary aid and called for the reinstatement of the democratically elected President Mohamed Bazoum.
The US offered support to Bazoum and warned the coup leaders that they were jeopardizing years of successful cooperation and hundreds of millions of dollars in assistance.
The Economic Community of West African States will meet on Sunday to discuss the coup, while French President Emmanuel Macron was due to chair a meeting on the matter.