The junta’s announcement said high-ranking west African politicians and “their international mentors” had made false allegations and attempted to derail a peaceful solution to the crisis in order to justify a military intervention.

It said Bazoum was being charged following his exchanges with these people. The statement did not identify specific western countries and did not specify a date for the trial.

Bazoum, Niger’s democratically elected president, was ousted by members of his presidential guard on 26 July and has since been under house arrest with his wife and son.

A junta spokesperson, Amadou Abdramane, announced on state television on Sunday night that the military regime had “gathered the necessary evidence to prosecute before competent national and international authorities the ousted president and his local and foreign accomplices for high treason and for undermining the internal and external security of Niger”.

People close to the president as well as those in his ruling party say the family’s electricity and water have been cut off and they are running out of food.

Bazoum told Human Rights Watch that his son needed to see a doctor because of a serious heart condition. But the junta said on Sunday that Bazoum was regularly seeing his doctor and that the last visit was on 12 August.

“After this visit the doctor raised no concerns about the state of health of the ousted president and members of his family,” Abdramane said.

The junta accused west African politicians and international partners of fuelling a disinformation campaign to discredit the junta.

International pressure is growing on the junta to release and reinstate Bazoum. Immediately after the coup, the west African regional bloc Ecowas gave the regime seven days to return him to power and threatened to use military force if it did not happen, but that deadline came and went with no action from either side.

Ecowas said last week that it had ordered the deployment of a “standby” military force for a potential intervention to restore Bazoum, although it remained unclear when or if it would enter the country.

A memo from Senegal’s security forces dated 11 August, seen by the Associated Press, indicated that the country had ordered a “regroupment” from bases in Senegal on Monday as part of its contribution to the Ecowas mission in Niger. It was unclear what exactly was ordered to move, or where it was going.

Previous attempts by Ecowas to speak with the junta have foundered, and its delegations have been barred from entering the country.

The African Union’s peace and security council is meeting on Monday to discuss Niger’s crisis and could overrule the decision if it feels that wider peace and security on the continent is threatened by an intervention.

The statement regarding prosecution came hours after religious mediators met with the coup leader Gen Abdourahamane Tchiani, who indicated his regime was open to a diplomatic breakthrough.

According to Nigerian Islamic scholar Sheikh Bala Lau, Tchiani “said their doors were open to explore diplomacy and peace in resolving the matter”, a day after Lau’s delegation held talks in Niger’s capital, Niamey.

Tchiani reportedly “claimed the coup was well intended” and that the plotters “struck to stave off an imminent threat that would have affected” Nigeria as well as Niger, according to Lau’s statement.

The Muslim leaders visited Niamey with the blessing of the Nigerian president, Bola Tinubu, who is also head of Ecowas.

The prospect of a military intervention to reinstate Bazoum has divided Ecowas members and drawn warnings from foreign powers including Russia and Algeria.

Niger’s neighbours Mali and Burkina Faso, also ruled by military governments who seized power in coups, have said an intervention would be tantamount to a declaration of war on them.

Agencies contributed to this report