Niger's ousted and detained President Mohamed Bazoum was seen by his doctor on Saturday, August 13, his entourage has said.

His medical checkup comes amid mounting concern over his health condition, at a time when religious leaders from Nigeria met the coup leaders to try to defuse the crisis.

According to a member of his entourage the physician had also brought food for President Bazoum, his wife, and son, AFP reports.

"He's fine, given the situation," the source told AFP.

The African Union had warned of the "worryingly poor conditions" Bazoum was being held in and urged his immediate release.

US Secretary of State Antony Blinken said he was "dismayed" by the military's refusal to release Bazoum's family as a "demonstration of goodwill."

Human Rights Watch (HRW) said it had spoken to the ousted president earlier this week, saying the treatment of Bazoum and his family was "inhuman and cruel."

"I'm not allowed to receive my family members (or), my friends who have been bringing food and other supplies to us," HRW quoted him as saying.

"My son is sick, has a serious heart condition, and needs to see a doctor," he said. "They've refused to let him get medical treatment."

A CNN report filed last week also indicated that Bazoum was being isolated and fed dry rice and pasta.