NIAMEY - Six Niger opposition figures, including a former government minister, were charged with "violating the security of the state" Tuesday and remanded in custody, their party said.
The six are close to parliament speaker Hama Amadou, seen by his followers as the principal rival of President Mahamadou Issoufou in presidential eledctions due in 2016.
Among the six are former health minister Soumana Sanda, former Niamey mayor Oumarou Dogari, retired army colonel Abdourahamane Saidou, Amadou Salah, an MP for the Nigerien Democratic Movement (Moden), told AFP.
Moden is headed by Amadou.
Salah said a judge had questioned 35 people, but 29 of them were later released due to lack of evidence.
The six others were detained at Kollo prison, south of the capital.
Since May 21, about 44 Moden activists have been arrested, he added.
Interior Minister Hassoumi Massaoudou said on May 24 that some 40 Moden militants had been arrested in the investigation into shots fired at the home of a member of parliament close to the government and a firebomb attack on the ruling party headquarters.
But Amadou said the arrests had been deliberately orchestrated "to organise reprisals against us at a later stage".
Niamey prosecutors said Saturday they were investigating claims by Amadou that an unidentified person had tried to poison him.