The political opposition and the civil society organisation Turning the Page (TLP) claimed that the strikes had resulted in far more casualties than the seven attackers claimed by the ministry.

Niger's defence ministry said the army carried out aerial strikes on October 24 after two policemen were killed in a "terrorist" attack targeting Tamou police station in Tillaberi region, bordering Burkina Faso.

Seven attackers were killed and 24 wounded in the response to the raid, which included air raids against a clandestine gold mine near Tamou, according to the defence ministry.

"People say the site has been bombed from everywhere" and "that bodies in very advanced state of decomposition litter the wells and surroundings", said Niger's Interior Minister Hamadou Adamou Souley, who visited the site on Saturday.

"This is not the case," he said, expressing outrage at the "figures of 150 to 1,000 deaths (which) have even been reported".

The bombing had only hit "hangars where the attackers had taken refuge... at the time of the strikes", he said.

TLP denounced the "massacre of dozens of gold miners" by army helicopters, and also called for an independent investigation.

The opposition said in a statement read to parliament that "it is urgent and imperative that all the light be shed... through an independent investigation".

On Wednesday, representatives of the NGO visited the victims of the aerial operation who were admitted to a Niamey hospital.

"The testimonies gathered raise more concerns and questions about the veracity of the information communicated by the minister of defence," TLP said.