Military leaders announced the move on state TV, naming 21 new ministers, media reported.
Ali Mahaman Lamine Zeine will lead the government, with generals from the new military governing council heading the defense and interior ministries, according to the decree.
It comes as West African leaders are set to meet on Thursday to mull military action against the junta, led by former Presidential Guard Commander Gen Abdourahmane Tchiani.
Important decisions are expected from the gathering in Nigeria's capital Abuja, according to a statement from the 15-nation Economic Community of West African States on Tuesday.
Ecowas has already imposed sanctions on the junta following the coup, which also prompted the EU and France to slash aid to the impoverished nation.
The bloc is expected to favour diplomacy over military action on the ground, which it has said is a “last resort”.
It had threatened to send troops into Niger if President Bazoum was not reinstated by last Sunday.
On Wednesday, UN Secretary General Antonio Guterres reiterated deep concerns for the well-being of Bazoum and his family, still confined to the presidential residence.
The President has told friends he is being kept in isolation, “deprived of any human contact,” and fed dry rice and pasta.
The possibility of a military intervention in Niger has sparked debate within Ecowas and prompted warnings from neighbouring nations and Russia.
Speaking before flying to Abuja on Wednesday, Guinea-Bissau's President Umaro Sissoco Embalo said the future of the bloc was at stake following coups in four member states, namely Mali, Guinea, Burkina Faso and Niger.
Mr Bazoum remained Niger's sole recognised president and coups must be banned, he added.
Niger's neighbours Mali and Burkina Faso, both ruled by military governments who seized power in coups, have said an intervention would be tantamount to a declaration of war against them.
It is the fifth coup to take place in Niger since it became independent from France in 1960.
President Bazoum's election in 2021 had helped Niger cement close ties with France and the United States, both crucial allies in the fight against growing extremism in the Sahel.
France has evacuated its citizens from Niger and suspended aid to the country, while Washington has suspended counter-terror operations and evacuated non-essential embassy staff and their families.
Experts and US officials have warned the coup will bolster terrorist groups active in the area and roll back gains made in counter-terrorism.
MNA/PR