Niger's military junta has announced plans to prosecute deposed President Mohamed Bazoum for high treason and undermining national security.
This is the latest sign that the junta intends to resist international pressure to return power to Mr Bazoum.
He has been held in the basement of his palace since the military staged a coup about three weeks ago.
Mr Bazoum was in "good spirits" despite being held in "difficult" conditions, his doctor said after a visit.
Saturday's visit was approved amid growing international demands for Mr Bazoum's release.
But in a sign that it is hardening its position, the junta said in a statement read out on state TV that it had gathered evidence to prosecute "the deposed president and his local and foreign accomplices for high treason and undermining the internal and external security of Niger".
It did not give further details.
Mr Bazoum, 63, is being held captive with his wife and son and there were growing concerns about their health.
Gen Abdourahmane Tchiani, the head of the presidential guards unit, declared himself Niger's new ruler on 26 July after overthrowing him.
The West African regional bloc Ecowas has threatened military action to reverse the coup, but it has so far failed to follow through on its 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.