The US and UN are concerned about the health and safety of Niger’s elected President Mohamed Bazoum, who has spent more than two weeks under house arrest.
“We are greatly worried about his health and his personal safety and the personal safety of his family,” a US state department spokesman said.
The Economic Community of West African States (ECOWAS) had given Niger’s coup leaders until Sunday to stand down.
ECOWAS officials are meeting later to decide what to do next.
UN Secretary General Antonio Guterres also said he was concerned, including about the reportedly “deplorable living conditions” the family were in.
Mr Bazoum was deposed on 26 July.
Earlier, Mr Bazoum’s party said he and his family were being detained under “cruel” and “inhumane” conditions, Reuters reported.
Since then, a military junta has ruled Niger while Mr Bazoum has been kept in the presidential palace. Members of the junta have made no comment about the ousted leader’s condition.
On Tuesday US Secretary of State Antony Blinken called Mr Bazoum assuring him of the US’s ongoing support, Washington said.
US State Department spokesman Matthew Miller added: “As time goes on, as he’s held in isolation, it’s a situation that is of growing concern to us.”
Mr Bazoum’s political party, PNDS-Tarayya, claimed in a statement that Mr Bazoum and his family had no access to running water, electricity, fresh goods or doctors.
The statement echoed previous comments made by Niger’s elected Prime Minister Ouhoumoudou Mahamadou, who has said Mr Bazoum was being held with his wife and son without electricity or water.
The head of the presidential guard, Gen Abdourahmane Tchiani, claims he now runs Niger, while the junta appointed ex-finance minister, Ali Mahaman Lamine Zeine, as the new prime minister following the coup.
The new military regime has also closed Niger’s airspace until further notice, citing the “threat of military intervention” from ECOWAS.
On Wednesday, France denied accusations from Niger’s military junta that it was trying to destabilise the country.
Coup leaders claimed French aircraft had breached the country’s airspace and French soldiers had freed captured jihadists in order to attack military positions.
“France firmly denies the new unfounded accusations by the putschists in Niger,” the French defence and foreign ministries said in a joint statement quoted by AFP news agency.
They added that the flight had been authorised by Niger’s military.
The junta in Niger say it will resist any “aggression” by ECOWAS and Western powers
Both the US and France operate military bases in Niger as part of operations to disrupt jihadist groups operating in the wider region.
Niger became the main base for French troops after they were told to leave Mali following a coup there.
