Niger's ousted President Mohamed Bazoum has been stripped of his immunity by the State Court of Niamey, a move that signals the ruling junta will launch criminal proceedings against him, his lawyers said on Friday.

Bazoum was toppled in a military coup last July. He and his wife have since been held in detention, despite repeated calls from the regional political and economic bloc ECOWAS and Western powers for his release.

One of his lawyers, Moussa Coulibaly, announced the court's decision in a statement and said it paved the way for the court to prosecute Bazoum for treason and conspiracy to undermine state security.

The court proceedings "violat(ed) the absolute rights of the defence: we were not authorised to meet our client and the court refused to hear our arguments," he added.

It was not immediately possible to reach the Niger authorities for comment. Last year, the junta said it would prosecute Bazoum for high treason over his exchanges with foreign heads of state and international organisations.

The coup, one of eight in West and Central Africa since 2020, swept the military authorities to power. They have ignored the calls for Bazoum's reinstatement, including from the ECOWAS Court of Justice, which last year ruled that his detention was arbitrary.

Bazoum's lawyers said he and his wife had never been brought before a magistrate. Their telephone line at the presidency was taken away in October, since when they have been cut off from the world with no visitors allowed apart from their doctor, lawyers said.

In January, Niger's military tribunal granted the ousted president's 23-year-old-son, Mohamed Bazoum Salem, provisional release from house arrest.