The military junta in Niger has announced preparations to charge ousted President Mohamed Bazoum with high treason and damaging national security.
This is the latest indication that the junta would reject international pressure to hand up control to Mr Bazoum.
When the military conducted a coup around three weeks ago, he has been detained in the basement of his palace.
Mr Bazoum was in “excellent spirits” despite being confined in “tough” conditions, according to his doctor.
The visit on Saturday was authorised despite mounting international pressure for Mr Bazoum’s release.
Nevertheless, in a hint that it is strengthening its stance, the junta stated in a statement aired on state television that it has acquired evidence to try “the ousted president and his local and international collaborators for high treason and compromising Niger’s internal and external security.”
It did not provide any other information.
Mr Bazoum, 63, is being held hostage alongside his wife and kid, and their health is deteriorating.
After toppling him, Gen Abdourahmane Tchiani, the leader of the presidential guards unit, declared himself Niger’s new ruler on July 26.
The West African regional organisation Ecowas has threatened military intervention to overthrow the coup, but has yet to execute on this threat.
The coup leaders have warned they will defend themselves against any intervention.
Ecowas has also imposed sanctions on the junta, including cutting electricity to Niger. This has caused blackouts in the capital Niamey, and other major cities.
On Saturday, a high-powered delegation of Muslim clerics from neighbouring Nigeria met junta leaders in Niamey in a bid to mediate an end to the crisis.
Junta-appointed Prime Minister Ali Mahamane Lamine Zeine said he was optimistic that talks with Ecowas would take place in the coming days “to discuss how the sanctions against us will be lifted”.
The coup in Niger mirrored similar takeovers in neighbouring Burkina Faso and Mali, amid an Islamist insurgency and a growing Russian influence in the wider Sahel region through its mercenary group Wagner.
Despite his captivity, Mr Bazoum was able to publish an article in The Washington Post stating that he was a hostage and that the coup would have “devastating consequences for our country, our region and the entire world”.
Mr Bazoum is reported to have lost a “worrying” amount of weight, while his 20-year-old son, who has a chronic medical condition, was also reportedly denied care.
UN human rights chief Volker Turk described the conditions of the detention as inhumane, degrading and in violation of international human rights law.
His daughter Zazia, 34, who was on holiday in France during the coup, told the UK-based Guardian newspaper last week that her father, mother and brother had no clean water or electricity and were living on rice and pasta.
Fresh food was rotting in the fridge because there was no power, she said.
Mr Bazoum has been seen once since he was overthrown, in a photo released after he met Chad’s leader Mahamat Idriss Déby Itno.
Mr Déby met both the junta and Mr Bazoum soon after the coup in a failed bid to resolve the crisis.
