Tchiani made his remarks on national television on Friday.
Officers of the presidential guard detained Niger President Mohamed Bazoum, elected in 2021, in his palace on Wednesday.
That evening, 10 military officers announced on television that the so-called National Council for the Safeguard of the Homeland (CNSP) had taken power.
All demonstrations were banned in the West African country of 26 million, the Interior Ministry said on Thursday.
“Our defence and security forces have decided to put an end to the regime that you know,’’ Col. Amadou Abdramane said on national television.
The army warned foreign states not to attempt a military intervention, saying it could have devastating consequences for the country.
Opposition parties are also backing the coup, according to a statement published on Nigerien media.
It remained unclear which and how many parties were behind it.
The authors called for demonstrations on Friday.
On Thursday there was sharp criticism in response to the power grab from Washington, the European Union, the African Union (AU) and individual governments, including Russia and Germany.
Berlin still has some 100 soldiers stationed in the country.
U.S. Secretary of State Antony Blinken also called for Bazoum’s immediate release and for the immediate respect for the rule of law and for public safety.
European Council President Charles Michel said he had spoken to Bazoum and assured him of EU’s support.
The EU condemned the destabilisation attempt in the strongest possible terms, he said.
The German Foreign Ministry echoed the call, saying “we are following events in Niger with great concern. We condemn the attempt by parts of the military to overturn Niger’s constitutional, democratic order.
“We call on these individuals to immediately release Bazoum, the country’s democratically-elected President, and to return to their quarters.”
Moscow also called on the military to release Bazoum, renounce violence and resolve all disputes through peaceful and constructive dialogue.
