A court in Niger has freed fifteen civilians accused of complicity in an attempted putsch against President Mahamadou Issoufou, their lawyer said on Saturday.

In December 2015, the government said it had foiled a coup and arrested people who planned to use aerial firepower to seize control of the West African country, a major Uranium producer and Western ally in the fight against Islamists in the Sahara.

The fifteen were freed on Friday. Nine military officers including the alleged ringleader General Salou Souleymane, are still behind bars awaiting trial.

"From the start we were convinced our clients are innocent," lawyer Ali Kadri said on private local TV station Bonferey. "There was no (evidence) ... to suggest that they were implicated in this affair," he said.

Issoufou was elected in 2011, one year after a coup. He was re-elected in February last year with 92.5 percent of the vote after the opposition coalition boycotted the polls.